CHAPTER I.

VOYAGE FROM NEW YORK TO RIO DE JANEIRO.

FIRST SUNDAY AT SEA.—GULF STREAM.—GULF-WEED.—LECTURES PROPOSED.—FIRST LECTURE: “ON THE GULF STREAM IN THE GULF STREAM.”—AQUARIUM ESTABLISHED ON BOARD.—SECOND LECTURE.—ROUGH SEA.—PECULIAR TINT OF WATER.—THIRD LECTURE: LAYING OUT WORK OF EXPEDITION IN BRAZIL; DISTRIBUTION OF FISHES IN BRAZILIAN RIVERS; ITS BEARING ON ORIGIN OF SPECIES; COLLECTING OF EGGS.—TROPICAL SUNSET.—FOURTH LECTURE: PLAN OF GEOLOGICAL INVESTIGATIONS WITH SPECIAL REFERENCE TO GLACIAL PHENOMENA IN SOUTH AMERICA.—FLYING-FISH.—FIFTH LECTURE: GLACIAL PHENOMENA, CONTINUED.—SECOND SUNDAY AT SEA.—ROUGH WATER.—SIXTH LECTURE: EMBRYOLOGICAL INVESTIGATIONS AS A GUIDE TO SOUND CLASSIFICATION.—SEVENTH LECTURE.—MOONLIGHT NIGHTS.—TRADE-WINDS.—EIGHTH LECTURE: IMPORTANCE OF PRECISION IN LOCALIZING SPECIMENS.—SOUTHERN CROSS.—NINTH LECTURE: FRESH-WATER FISHES OF BRAZIL.—EASTER SUNDAY.—FIRST SIGHT OF SOUTH AMERICAN SHORE.—OLINDA.—PERNAMBUCO.—CATAMARANS.—TENTH LECTURE: METHODS OF COLLECTING.—ELEVENTH LECTURE: CLASSIFICATION OF FISHES, AS ILLUSTRATED BY EMBRYOLOGY.—PREPARATIONS FOR ARRIVAL.—TWELFTH LECTURE: PRACTICAL LESSON IN EMBRYOLOGY—CLOSING LECTURE: TRANSMUTATION THEORY; INTELLECTUAL AND POLITICAL INDEPENDENCE.—RESOLUTIONS AND SPEECHES.—SINGULAR RED PATCHES ON THE SURFACE OF THE SEA.

_April 2d, 1865._—Our first Sunday at sea. The weather is delicious, the ship as steady as anything on the water can be, and even the most forlorn of our party have little excuse for sea-sickness. We have had service from Bishop Potter this morning, and since then we have been on deck reading, walking, watching a singular cloud, which the captain says is a cloud of smoke, in the direction of Petersburg. We think it may be the smoke of a great decisive engagement going on while we sail peacefully along. What it means, or how the battle ends, if battle it be, we shall not know for two months perhaps.[2] Mr. Agassiz is busy to-day in taking notes, at regular intervals, of the temperature of the water, as we approach the Gulf Stream. To-night we cut it at right angles, and he will remain on deck to continue his observations.

_April 3d._—The Professor sat up last night as he intended, and found his watch, which was shared by one or two of his young assistants, very interesting. We crossed the Gulf Stream opposite Cape Hatteras, at a latitude where it is comparatively narrow, some sixty miles only in breadth. Entering it at about six o’clock, we passed out of it a little after midnight. The western boundary of the warm waters stretching along the coast had a temperature of about 57°. Immediately after entering it, the temperature began to rise gradually, the maximum being about 74°, falling occasionally, however, when we passed through a cold streak, to 68°. These cold streaks in the Gulf Stream, which reach to a considerable depth, the warm and cold waters descending together in immediate contact for at least a hundred fathoms, are attributed by Dr. Bache to the fact that the Gulf Stream is not stationary. It sways as a whole sometimes a little toward the shore, sometimes a little away from it, and, in consequence of this, the colder water from the coast creeps in, forming these vertical layers in its midst. The eastern boundary is warmer than the western one, for the latter is chilled by the Arctic currents, which form a band of cold water all along the Atlantic shore. Their influence is felt nearly to the latitude of Florida. On coming out of the Gulf Stream the temperature of the water was 68°, and so it continued for an hour longer, after which Mr. Agassiz ceased his observations. To-day some of the gulf-weed was gathered by a sailor, and we found it crowded with life. Hydroids, in numbers, had their home upon it; the delicate branching plumularia and a pretty campanularia, very like some of our New England species; beside these, bryozoa, tiny compound mollusks, crusted its stem, and barnacles were abundant upon it. These are all the wonders that the deep has yielded us to-day, though the pretty Portuguese men-of-war go floating by the vessel, out of reach thus far. Such are the events of our life: we eat and drink and sleep, read, study Portuguese, and write up our journals.

_April 4th._—It has occurred to Mr. Agassiz, as a means of preparing the young men who accompany him for the work before them, to give a course of lectures on ship-board. Some preparation of the kind is the more necessary, since much of the work must be done independently of him, as it will be impossible for so large a party to travel together; and the instructions needed will be more easily given in a daily lecture to all, than in separate conversations with each one singly. The idea finds general favor. The large saloon makes an excellent lecture-room; a couple of leaves from the dining-table with a black oil-cloth stretched across them serve as a blackboard. The audience consists, not only of our own company, but includes the few ladies who are on board, Mr. Bradbury, the captain of our steamer, Bishop Potter, some of the ship’s officers, and a few additional passengers, all of whom seem to think the lecture a pleasant break in the monotony of a sea voyage. To-day the subject was naturally suggested by the seaweeds of the Gulf Stream, so recently caught and so crowded with life,—“A lecture on the Gulf Stream in the Gulf Stream,” as one of the listeners suggests. It was opened, however, by a few words on the exceptional character of the position of this scientific commission on board the Colorado.

“Fifty years ago, when naturalists carried their investigations to distant lands, either government was obliged to provide an expensive outfit for them, or, if they had no such patronage, scanty opportunities grudgingly given might be granted them on ordinary conveyances. Even if such accommodation were allowed them, their presence was looked upon as a nuisance: no general interest was felt in their objects; it was much if they were permitted, on board some vessel, to have their bucket of specimens in a corner, which any sailor might kick over, unreproved, if it chanced to stand in his way. This ship, and the spirit prevailing in her command, opens to me a vista such as I never dreamed of till I stood upon her deck. Here, in place of the meagre chances I remember in old times, the facilities could hardly be greater if the ship had been built as a scientific laboratory. If any such occasion has ever been known before, if any naturalist has ever been treated with such consideration, and found such intelligent appreciation of his highest aims, on board a merchant-ship fitted up for purposes of trade, I am not aware of it. I hope the first trip of the Colorado will be remembered in the annals of science. I, at least, shall know whom to thank for an opportunity so unique. This voyage, and the circumstances connected with it, are, to me, the signs of a good time coming; when men of different interests will help each other; when naturalists will be more liberal and sailors more cultivated, and natural science and navigation will work hand in hand. And now for my lecture,—my first lecture on ship-board.”

The lecture was given, of course, specimen in hand, the various inhabitants of the branch of seaweed giving their evidence in succession of their own structure and way of life. To these living illustrations were added drawings on the blackboard to show the transformations of the animals, their embryological history, &c.[3] Since the lecture, Captain Bradbury has fitted up a large tank as an aquarium, where any specimens taken during the voyage may be preserved and examined. Mr. Agassiz is perfectly happy, enjoying every hour of the voyage, as well he may, surrounded as he is with such considerate kindness.

_April 6th._—Though I took notes, as usual, of the lecture yesterday, I had not energy enough to enter them in my journal. The subject was the Gulf Stream,—the stream itself this time, not the animals it carries along with it. Mr. Agassiz’s late observations, though deeply interesting to himself, inasmuch as personal confirmation of facts already known is always satisfactory, have nothing novel now-a-days; yet the history of the facts connected with the discovery of the Gulf Stream, and their gradual development, is always attractive, and especially so to Americans, on account of its direct connection with scientific investigations carried on under our government. Mr. Agassiz gave a slight sketch of this in opening his lecture. “It was Franklin who first systematically observed these facts, though they had been noticed long before by navigators. He recorded the temperature of the water as he left the American continent for Europe, and found that it continued cold for a certain distance, then rose suddenly, and after a given time sank again to a lower temperature, though not so low as before. With the comprehensive grasp of mind characteristic of all his scientific results, he went at once beyond his facts. He inferred that the warm current, keeping its way so steadily through the broad Atlantic, and carrying tropical productions to the northern shores of Europe, must take its rise in tropical regions, must be heated by a tropical sun.[4] This was his inference: to work it out, to ascertain the origin and course of the Gulf Stream, has been, in a great degree, the task of the United States Coast Survey, under the direction of his descendant, Dr. Bache.”[5]

We are now fairly in the tropics. “The trades” blow heavily, and yesterday was a dreary day for those unused to the ocean; the beautiful blue water, of a peculiar metallic tint, as remarkable in color, it seemed to me, as the water of the Lake of Geneva, did not console us for the heavy moral and physical depression of sea-sick mortals. To-day the world looks brighter; there is a good deal of motion, but we are more accustomed to it. This morning the lecture had, for the first time, a direct bearing upon the work of the expedition. The subject was, “How to observe, and what are the objects of scientific explorations in modern times.”

“My companions and myself have come together so suddenly and so unexpectedly on our present errand, that we have had little time to organize our work. The laying out of a general scheme of operations is, therefore, the first and one of the most important points to be discussed between us. The time for great discoveries is passed. No student of nature goes out now expecting to find a new world, or looks in the heavens for any new theory of the solar system. The work of the naturalist, in our day, is to explore worlds the existence of which is already known; to investigate, not to discover. The first explorers, in this modern sense, were Humboldt in the physical world, Cuvier in natural history, Lavoisier in chemistry, La Place in astronomy. They have been the pioneers in the kind of scientific work characteristic of our century. We who have chosen Brazil as our field must seek to make ourselves familiar with its physical features, its mountains and its rivers, its animals and plants. There is a change, however, to be introduced in our mode of work, as compared with that of former investigators. When less was known of animals and plants the discovery of new species was the great object. This has been carried too far, and is now almost the lowest kind of scientific work. The discovery of a new species as such does not change a feature in the science of natural history, any more than the discovery of a new asteroid changes the character of the problems to be investigated by astronomers. It is merely adding to the enumeration of objects. We should look rather for the fundamental relations among animals; the number of species we may find is of importance only so far as they explain the distribution and limitation of different genera and families, their relations to each other and to the physical conditions under which they live. Out of such investigations there looms up a deeper question for scientific men, the solution of which is to be the most important result of their work in coming generations. The origin of life is the great question of the day. How did the organic world come to be as it is? It must be our aim to throw some light on this subject by our present journey. How did Brazil come to be inhabited by the animals and plants now living there? Who were its inhabitants in past times? What reason is there to believe that the present condition of things in this country is in any sense derived from the past? The first step in this investigation must be to ascertain the geographical distribution of the present animals and plants. Suppose we first examine the Rio San Francisco. The basin of this river is entirely isolated. Are its inhabitants, like its waters, completely distinct from those of other basins? Are its species peculiar to itself, and not repeated in any other river of the continent? Extraordinary as this result would seem, I nevertheless expect to find it so. The next water-basin we shall have to examine will be that of the Amazons, which connects through the Rio Negro with the Orinoco. It has been frequently repeated that the same species of fish exist in the waters of the San Francisco and in those of Guiana and of the Amazons. At all events, our works on fishes constantly indicate Brazil and Guiana as the common home of many species; but this observation has never been made with sufficient accuracy to merit confidence. Fifty years ago the exact locality from which any animal came seemed an unimportant fact in its scientific history, for the bearing of this question on that of origin was not then perceived. To say that any specimen came from South America was quite enough; to specify that it came from Brazil, from the Amazons, the San Francisco, or the La Plata, seemed a marvellous accuracy in the observers. In the museum at Paris, for instance, there are many specimens entered as coming from New York or from Pará; but all that is absolutely known about them is that they were shipped from those sea-ports. Nobody knows exactly where they were collected. So there are specimens entered as coming from the Rio San Francisco, but it is by no means sure that they came exclusively from that water-basin. All this kind of investigation is far too loose for our present object. Our work must be done with much more precision; it must tell something positive of the geographical distribution of animals in Brazil. Therefore, my young friends who come with me on this expedition, let us be careful that every specimen has a label, recording locality and date, so secured that it shall reach Cambridge safely. It would be still better to attach two labels to each specimen, so that, if any mischance happens to one, our record may not be lost. We must try not to mix the fishes of different rivers, even though they flow into each other, but to keep our collections perfectly distinct. You will easily see the vast importance of thus ascertaining the limitation of species, and the bearing of the result on the great question of origin.

“Something is already known. It is ascertained that the South American rivers possess some fishes peculiar to them. Were these fishes then created in these separate water-systems as they now exist, or have they been transferred thither from some other water-bed? If not born there, how did they come there? Is there, or has there ever been, any possible connection between these water-systems? Are their characteristic species repeated elsewhere? Thus we narrow the boundaries of the investigation, and bring it, by successive approaches, nearer the ultimate question. But the first inquiry is, How far are species distinct all over the world, and what are their limits? Till this is ascertained, all theories about their origin, their derivation from one another, their successive transformation, their migration from given centres, and so on, are mere beating about the bush. I allude especially to the fresh-water fishes, in connection with this investigation, on account of the precision of their boundaries. Looking at the matter theoretically, without a positive investigation, I do not expect to find a single species of the Lower Amazons above Tabatinga.[6] I base this supposition upon my own observations respecting the distribution of species in the European rivers. I have found that, while some species occur simultaneously in the many upper water-courses which combine to form the Rhine, the Rhone, and the Danube, most of them are not found in the lower course of these rivers; that, again, certain species are found in two of these water-basins and do not occur in the third, or inhabit only one and are not to be met in the two others. The brook trout, for instance (_Salmo Fario_), is common to the upper course and the higher tributaries of all the three river-systems, but does not inhabit the main bed of their lower course. So it is, also, and in a more striking degree, with the Salmling (_Salmo Salvelinus_). The Huchen (_Salmo Hucho_) is only found in the Danube. But the distribution of the perch family in these rivers is, perhaps, the most remarkable. The Zingel (_Aspro Zingel_) and the Schrætzer (_Acerina Schrætzer_) are only found in the Danube; while _Acerina cernua_ is found in the Danube as well as in the Rhine, but not in the Rhone; and _Aspro asper_ in the Danube as well as in the Rhone, but not in the Rhine. The Sander (_Lucioperca Sandra_) is found in the Danube and the other large rivers of Eastern Europe, but occurs neither in the Rhine nor in the Rhone. The common perch (_Perca fluviatilis_), on the contrary, is found both in the Rhine and Rhone, but not in the Danube, which, however, nourishes another species of true Perca, already described by Schaeffer as _Perca vulgaris_. Again, the pickerel (_Esox Lucius_) is common to all these rivers, especially in their lower course, and so is also the cusk (_Lota vulgaris_). The special distribution of the carp family would afford many other striking examples, but they are too numerous and too little known to be used as an illustration here.

“This is among the most remarkable instances of what I would call the arbitrary character of geographical distribution. Such facts cannot be explained by any theory of accidental dispersion, for the upper mountain rivulets, in which these great rivers take their rise, have no connection with each other; nor can any local circumstance explain the presence of some species in all the three basins, while others appear only in one, or perhaps in two, and are absent from the third, or the fact that certain species inhabiting the head-waters of these streams are never found in their lower course when the descent would seem so natural and so easy. In the absence of any positive explanation, we are left to assume that the distribution of animal life has primary laws as definite and precise as those which govern anything else in the system of the universe.

“It is for the sake of investigations of this kind that I wish our party to divide, in order that we may cover as wide a ground as possible, and compare a greater number of the water-basins of Brazil. I wish the same to be done, as far as may be, for all the classes of Vertebrates, as well as for Mollusks, Articulates, and Radiates. As we have no special botanist in the party, we must be content to make a methodical collection of the most characteristic families of trees, such as the palms and tree ferns. A collection of the stems of these trees would be especially important as a guide to the identification of fossil woods. Much more is known of the geographical distribution of plants than of animals, however, and there is, therefore, less to be done that is new in that direction.

“Our next aim, and with the same object, namely, its bearing upon the question of origin, will be the study of the young, the collecting of eggs and embryos. This is the more important, since museums generally show only adult specimens. As far as I know, the Zoölogical Museum at Cambridge is the only one containing large collections of embryological specimens from all the classes of the animal kingdom. One significant fact, however, is already known. In their earliest stages of growth all animals of the same class are much more alike than in their adult condition, and sometimes so nearly alike as hardly to be distinguished. Indeed, there is an early period when the resemblances greatly outweigh the differences. How far the representatives of different classes resemble one another remains to be ascertained with precision. There are two possible interpretations of these facts. One is that animals so nearly identical in the beginning must have been originally derived from one germ, and are but modifications or transmutations, under various physical conditions, of this primitive unit. The other interpretation, founded on the same facts, is, that since, notwithstanding this material identity in the beginning, no germ ever grows to be different from its parent, or diverges from the pattern imposed upon it at its birth, therefore some other cause besides a material one must control its development; and if this be so, we have to seek an explanation of the differences between animals outside of physical influences. Thus far both these views rest chiefly upon personal convictions and opinions. The true solution of the problem must be sought in the study of the development of the animals themselves, and embryology is still in its infancy; for, though a very complete study of the embryology of a few animals has been made, yet these investigations include so small a number of representatives from the different classes of the animal kingdom that they do not yet give a basis for broad generalizations. Very little is known of the earlier stages in the formation of hosts of insects whose later metamorphoses, including the change of the already advanced larva, first to the condition of a chrysalis and then to that of a perfect insect, have been carefully traced. It remains to be ascertained to what extent the caterpillars of different kinds of butterflies, for instance, resemble one another during the time of their formation in the egg. An immense field of observation is open in this order alone.

“I have, myself, examined over one hundred species of bird embryos, now put up in the museum of Cambridge, and found that, at a certain age, they all have bills, wings, legs, feet, &c., &c. exactly alike. The young robin and the young crow are web-footed, as well as the duck. It is only later that the fingers of the foot become distinct. How very interesting it will be to continue this investigation among the tropical birds!—to see whether, for instance, the toucan, with its gigantic bill, has, at a certain age, a bill like that of all other birds; whether the spoonbill ibis has, at the same age, nothing characteristic in the shape of its bill. No living naturalist could now tell you one word about all this; neither could he give you any information about corresponding facts in the growth of the fishes, reptiles, or quadrupeds of Brazil, not one of the young of these animals having ever been compared with the adult. In these lectures I only aim at showing you what an extensive and interesting field of investigation opens before us; if we succeed in cultivating even a few corners of it we shall be fortunate.”

In the evening, which is always the most enjoyable part of our day, we sat on the guards and watched the first tropical sunset we had yet seen. The sun went down in purple and gold, and, after its departure, sent back a glow that crimsoned the clouds almost to the zenith, dying off to paler rose tints on the edges, while heavy masses of gray vapor, just beginning to be silvered by the moon, swept up from the south.

_April 7th._—To-day the lecture was upon the physical features of South America, something with reference to the geological and geographical work in which Mr. Agassiz hopes to have efficient aid from his younger assistants. So much of the lecture consisted of explanations given upon geological maps that it is difficult to record it. Its principal object, however, was to show in what direction they should work in order to give greater precision to the general information already secured respecting the formation of the continent. “The basin of the Amazons, for instance, is a level plain. The whole of it is covered with loose materials. We must watch carefully the character of these loose materials, and try to track them to their origin. As there are very characteristic rocks in various parts of this plain, we shall have a clew to the nature of at least some portion of these materials. My own previous studies have given me a special interest in certain questions connected with these facts. What power has ground up these loose materials? Are they the result of disintegration of the rock by ordinary atmospheric agents, or are they caused by the action of water, or by that of glaciers? Was there ever a time when large masses of ice descended far lower than the present snow line of the Andes, and, moving over the low lands, ground these materials to powder? We know that such an agency has been at work on the northern half of this hemisphere. We have now to look for its traces on the southern half, where no such investigations have ever been made within its warm latitudes; though to Darwin science is already indebted for much valuable information concerning the glacial phenomena of the temperate and colder portions of the South American continent. We should examine the loose materials in every river we ascend, and see what relation they bear to the dry land above. The color of the water in connection with the nature of the banks will tell us something. The waters of the Rio Branco, for instance, are said to be milky white; those of the Rio Negro, black. In the latter case the color is probably owing to the decomposition of vegetation. I would advise each one of our parties to pass a large amount of water from any river or stream along which they travel through a filter, and to examine the deposit microscopically. They will thus ascertain the character of the detritus, whether from sand, or lime, or granite, or mere river mud formed by the decomposition of organic matter. Even the smaller streams and rivulets will have their peculiar character. The Brazilian table-land rises to a broad ridge running from west to east, and determining the direction of the rivers. It is usually represented as a mountain range, but is in fact nothing but a high flat ridge serving as a water-shed, and cut transversely by deep fissures in which the rivers flow. These fissures are broad in their lower parts, but little is known of their upper range; and whoever will examine their banks carefully will do an important work for science. Indeed, very little is known accurately of the geology of Brazil. On the geological maps almost the whole country is represented as consisting of granite. If this be correct, it is very inconsistent with what we know of the geological structure of other continents, where the stratified rocks are in much larger proportions.”

Upon this followed some account of the different kinds of valley formation and of terraces. “Do the old terraces above the rivers of South America correspond to the river terraces on any of our rivers,—those of the Connecticut, for instance,—showing that their waters had formerly a much greater depth and covered a much wider bottom? There must of course have been a cause for this great accumulation of water in ancient periods. I account for it in the northern half of the hemisphere by the melting of vast masses of ice in the glacial period, causing immense freshets. There is no trustworthy account of the river terraces in Brazil. Bates, however, describes flat-topped hills between Santarem and Pará in the narrow part of the valley, near Almeyrim, rising 800 feet above the present level of the Amazons. If this part of the valley were flooded in old times, banks might have been formed of which these hills are a remnant. But because such a theory might account for the facts it does not follow that the theory is true. Our work must be to study the facts, to see, among other things, of what these hills are built, whether of rock or of loose materials. No one has told us anything as yet of their geological constitution.”[7]

To-day we have seen numbers of flying-fish from the deck, and were astonished at the grace and beauty of their motion, which we had supposed to be rather a leap than actual flight. And flight indeed it is not, their pectoral fins acting as sails rather than wings, and carrying them along on the wind. They skim over the water in this way to a great distance. Captain Bradbury told us he had followed one with his glass and lost sight of it at a considerable distance, without seeing it dip into the water again. Mr. Agassiz has great delight in watching them.[8] Having never before sailed in tropical seas, he enjoys every day some new pleasure.

_April 9th._—Yesterday Mr. Agassiz lectured upon the traces of glaciers as they exist in the northern hemisphere, and the signs of the same kind to be sought for in Brazil. After a sketch of what has been done in glacial investigation in Europe and the United States, showing the great extension of ice over these regions in ancient times, he continued as follows: “When the polar half of both hemispheres was covered by such an ice shroud, the climate of the whole earth must have been different from what it is now. The limits of the ancient glaciers give us some estimate of this difference, though of course only an approximate one. A degree of temperature in the annual average of any given locality corresponds to a degree of latitude; that is, a degree of temperature is lost for every degree of latitude as we travel northward, or gained for every degree of latitude as we travel southward. In our times, the line at which the average annual temperature is 32°, that is, at which glaciers may be formed, is in latitude 60° or thereabouts, the latitude of Greenland; while the height at which they may originate in latitude 45° is about 6,000 feet. If it appear that the ancient southern limit of glaciers is in latitude 36°, we must admit that in those days the present climate of Greenland extended to that line. Such a change of climate with reference to latitude must have been attended by a corresponding change of climate with reference to altitude. Three degrees of temperature correspond to about one thousand feet of altitude. If, therefore, it is found that the ancient limit of glacier action descends on the Andes, for instance, to 7,000 feet above the level of the sea under the equator, the present line of perpetual snow being at 15,000, it is safe to infer that in those days the climate was some 24° or thereabouts below its present temperature. That is, the temperature of the present snow line then prevailed at a height of 7,000 feet above the sea level, as the present average temperature of Greenland then prevailed in latitude 36°. I am as confident that we shall find these indications at about the limit I have pointed out as if I had already seen them. I would even venture to prophesy that the first moraines in the valley of the Marañon should be found where it bends eastward above Jaen.”[9]

Although the weather is fine, the motion of the ship continues to be so great that those of us who have not what are popularly called “sea-legs,” have much ado to keep our balance. For my own part, I am beginning to feel a personal animosity to “the trades.” I had imagined them to be soft, genial breezes wafting us gently southward; instead of which they blow dead ahead all the time, and give us no rest night or day. And yet we are very unreasonable to grumble; for never were greater comforts and conveniences provided for voyagers on the great deep than are to be found on this magnificent ship. The state-rooms large and commodious, parlor and dining-hall well ventilated, cool, and cheerful, the decks long and broad enough to give a chance for extensive “constitutionals” to everybody who can stand upright for two minutes together, the attendance punctual and admirable in every respect; in short, nothing is left to be desired except a little more stable footing.

_April 10th._—A rough sea to-day, notwithstanding which we had our lecture as usual, though I must say, that, owing to the lurching of the ship, the lecturer pitched about more than was consistent with the dignity of science. Mr. Agassiz returned to the subject of embryology, urging upon his assistants the importance of collecting materials for this object as a means of obtaining an insight into the deeper relations between animals.

“Heretofore classification has been arbitrary, inasmuch as it has rested mainly upon the interpretation given to structural differences by various observers, who did not measure the character and value of these differences by any natural standard. I believe that we have a more certain guide in these matters than opinion or the individual estimate of any observer, however keen his insight into structural differences. The true principle of classification exists in Nature herself, and we have only to decipher it. If this conviction be correct, the next question is, How can we make this principle a practical one in our laboratories, an active stimulus in our investigations? Is it susceptible of positive demonstration in material facts? Is there any method to be adopted as a correct guide, if we set aside the idea of originating systems of classification of our own, and seek only to read that already written in nature? I answer, Yes. The standard is to be found in the changes animals undergo from their first formation in the egg to their adult condition.

“It would be impossible for me here and now to give you the details of this method of investigation, but I can tell you enough to illustrate my statement. Take a homely and very familiar example, that of the branch of Articulates. Naturalists divide this branch into three classes,—Insects, Crustacea, and Worms; and most of them tell you that Worms are lowest, Crustacea next in rank, and that Insects stand highest, while others have placed the Crustacea at the head of the group. We may well ask why. Why does an insect stand above a crustacean, or, _vice versa_, why is a grasshopper or a butterfly structurally superior to a lobster or a shrimp? And indeed there must be a difference in opinion as to the respective standing of these groups so long as their classification is allowed to remain a purely arbitrary one, based only upon interpretation of anatomical details. One man thinks the structural features of Insects superior, and places them highest; another thinks the structural features of the Crustacea highest, and places them at the head. In either case it is only a question of individual appreciation of the facts. But when we study the gradual development of the insect, and find that in its earliest stages it is worm-like, in its second, or chrysalis stage, it is crustacean-like, and only in its final completion it assumes the character of a perfect insect, we have a simple natural scale by which to estimate the comparative rank of these animals. Since we cannot suppose that there is a retrograde movement in the development of any animal, we must believe that the insect stands highest, and our classification in this instance is dictated by Nature herself. This is one of the most striking examples, but there are others quite as much so, though not as familiar. The frog, for instance, in its successive stages of development, illustrates the comparative standing of the orders composing the class to which it belongs. These orders are differently classified by various naturalists, according to their individual estimate of their structural features. But the growth of the frog, like that of the insects, gives us the true grade of the type.[10] There are not many groups in which this comparison has been carried out so fully as in the insects and frogs; but wherever it has been tried it is found to be a perfectly sure test. Occasional glimpses of these facts, seen disconnectedly, have done much to confirm the development theory, so greatly in vogue at present, though under a somewhat new form. Those who sustain these views have seen that there was a gradation between animals, and have inferred that it was a material connection. But when we follow it in the growth of the animals themselves, and find that, close as it is, no animal ever misses its true development, or grows to be anything but what it was meant to be, we are forced to admit that the gradation which unquestionably unites all animals is an intellectual, not a material one. It exists in the Mind which made them. As the works of a human intellect are bound together by mental kinship, so are the thoughts of the Creator spiritually united. I think that considerations like these should be an inducement for us all to collect the young of as many animals as possible on this journey. In so doing we may change the fundamental principles of classification, and confer a lasting benefit on science.

“It is very important to select the right animals for such investigations. I can conceive that a lifetime should be passed in embryological studies, and yet little be learned of the principles of classification. The embryology of the worm, for instance, would not give us the natural classification of the Articulates, because we should see only the first step of the series; we should not reach the sequence of the development. It would be like reading over and over again the first chapter of a story. The embryology of the Insects, on the contrary, would give us the whole succession of a scale on the lowest level of which the Worms remain forever. So the embryology of the frog will give us the classification of the group to which it belongs, but the embryology of the Cecilia, the lowest order in the group, will give us only the initiatory steps. In the same way the naturalist who, in studying the embryology of the reptiles, should begin with their lowest representatives, the serpents, would make a great mistake. But take the alligator, so abundant in the regions to which we are going. An alligator’s egg in the earliest condition of growth has never been opened by a naturalist. The young have been occasionally taken from the egg just before hatching, but absolutely nothing is known of their first phases of development. A complete embryology of the alligator would give us not only the natural classification of reptiles as they exist now, but might teach us something of their history from the time of their introduction upon earth to the present day. For embryology shows us not only the relations of existing animals to each other, but their relations to extinct types also. One prominent result of embryological studies has been to show that animals in the earlier stages of their growth resemble ancient representatives of the same type belonging to past geological ages. The first reptiles were introduced in the carboniferous epoch, and they were very different from those now existing. They were not numerous at that period; but later in the world’s history there was a time, justly called the ‘age of reptiles,’ when the gigantic Saurians, Plesiosaurians, and Ichthyosaurians abounded. I believe, and my conviction is drawn from my previous embryological studies, that the changes of the alligator in the egg will give us the clew to the structural relations of the Reptiles from their first creation to the present day,—will give us, in other words, their sequence in time as well as their sequence in growth. In the class of Reptiles, then, the most instructive group we can select with reference to the structural relations of the type as it now exists, and their history in past times, will be the alligator. We must therefore neglect no opportunity of collecting their eggs in as large numbers as possible.

“There are other animals in Brazil, low in their class to be sure, but yet very important to study embryologically, on account of their relation to extinct types. These are the sloths and armadillos,—animals of insignificant size in our days, but anciently represented in gigantic proportions. The Megatherium, the Mylodon, the Megalonyx, were some of these immense Mammalia. I believe that the embryonic changes of the sloths and armadillos will explain the structural relations of those huge Edentata and their connection with the present ones. South America teems with the fossil bones of these animals, which indeed penetrated into the northern half of the hemisphere as high up as Georgia and Kentucky, where their remains have been found. The living representatives of the family are also numerous in South America, and we should make it one of our chief objects to get specimens of all ages and examine them from their earliest phases upward. We must, above all, try not to be led away from the more important aims of our study by the diversity of objects. I have known many young naturalists to miss the highest success by trying to cover too much ground,—by becoming collectors rather than investigators. Bitten by the mania for amassing a great number and variety of species, such a man never returns to the general consideration of more comprehensive features. We must try to set before ourselves certain important questions, and give ourselves resolutely to the investigation of these points, even though we should sacrifice less important things more readily reached.

“Another type full of interest, from an embryological point of view, will be the Monkeys. Since some of our scientific colleagues look upon them as our ancestors, it is important that we should collect as many facts as possible concerning their growth. Of course it would be better if we could make the investigation in the land of the Orangs, Gorillas, and Chimpanzees,—the highest monkeys and the nearest to man in their development. Still even the process of growth in the South American monkey will be very instructive. Give a mathematician the initial elements of a series, and he will work out the whole; and so I believe when the laws of embryological development are better understood, naturalists will have a key to the limits of these cycles of growth, and be able to appoint them their natural boundaries even from partial data.

“Next in importance I would place the Tapirs. This is one of a family whose geological antecedents are very important and interesting. The Mastodons, the Palæotherium, the Dinotherium, and other large Mammalia of the Tertiaries, are closely related to the Tapir. The elephant, rhinoceros, and the like, are of the same family. From its structural standing next to the elephant, which is placed highest in the group, the embryology of the Tapir would give us a very complete series of changes. It would seem from some of the fossil remains of this family that the Pachyderms were formerly more nearly related to the Ruminants and Rodents than they now are. Therefore it would be well to study the embryology of the Capivari, the Paca, and the Peccary, in connection with that of the Tapir. Lastly, it will be important to learn something of the embryology of the Manatee or Sea-Cow of the Amazons. It is something like a porpoise in outline, and seems to be the modern representative of the ancient Dinotherium.”

_April 12th._—The lecture to-day was addressed especially to the ornithologists of the party, its object being to show how the same method of study,—that of testing the classification by the phases of growth in the different groups,—might be applied to the birds as profitably as to other types.

We have made good progress in the last forty-eight hours, and are fast leaving our friends “the trades” behind. The captain promises us smooth waters in a day or two. With the dying away of the wind will come greater heat, but as yet we have had no intensely warm weather. The sun, however, keeps us within doors a great part of the day, but in the evening we sit on the guards, watch the sunset over the waters, and then the moonlight, and so while away the time till nine or ten o’clock, when one by one the party disperses. The sea has been so rough that we have not been able to capture anything, but when we get into smoother waters, our naturalists will be on the look out for jelly-fish, argonautas, and the like.

_April 13th._—In to-day’s lecture Mr. Agassiz returned again to the subject of geographical distribution and the importance of localizing the collections with great precision.

“As Rio de Janeiro is our starting-point, the water-system in its immediate neighborhood will be as it were a schoolroom for us during the first week of our Brazilian life. We shall not find it so easy a matter as it seems to keep our collections distinct in this region. The head-waters of some of the rivers near Rio, flowing in opposite directions, are in such close proximity that it will be difficult sometimes to distinguish them. Outside of the coast range, to which the Organ Mountains belong, are a number of short streams, little rills, so to speak, emptying directly into the ocean. It will be important to ascertain whether the same animals occur in all these short water-courses. I think this will be found to be the case, because it is so with corresponding small rivers on our northern coast. There are little rivers along the whole coast from Maine to New Jersey; all these disconnected rivers contain a similar fauna. There is another extensive range inland of the coast ridge, the Serra de Mantiquera, sloping gently down to the ocean south of the Rio Belmonte or Jequitinhonha. Rivers arising in this range are more complex; they have large tributaries. Their upper part is usually broken by waterfalls, their lower course being more level; probably in the lower courses of these rivers we shall find fishes similar to those of the short coast streams, while in the higher broken waters we shall find distinct faunæ.” The lecture closed with some account of the excursions likely to be undertaken in the neighborhood of Rio de Janeiro on arriving, and with some practical instructions about collecting, based upon Mr. Agassiz’s personal experience.[11]

_April 14th._—Last evening was the most beautiful we have had since we left home; perfectly clear with the exception of soft white masses of cloud on the horizon, all their edges silvered by the moonlight. We looked our last for many months to come on the north star, and saw the southern cross for the first time. With the visible image I lost a far more wonderful constellation which had lived in my imagination; it has vanished with all its golden glory, a celestial vision as amazing as that which converted Constantine, and in its place stands the veritable constellation with its four little points of light.

The lecture to-day was upon the fishes of South America. “I will give you this morning a slight sketch of the characteristic fishes in South America, as compared with those of the Old World and North America. Though I do not know how the fishes are distributed in the regions to which we are going, and it is just upon the investigation of this point that I want your help, I know their character as distinguished from those of other continents. We must remember that the most important aim of all our studies in this direction will be the solution of the question whether any given fauna is distinct and has originated where it now exists. To this end I shall make you acquainted with the Brazilian animals so far as I can in the short time we have before beginning our active operations, in order that you may be prepared to detect the law of their geographical distribution. I shall speak to-day more especially of the fresh-water fishes.

“In the northern hemisphere there is a remarkable group of fishes known as the Sturgeons. They are chiefly found in the waters flowing into the Polar seas, as the Mackenzie River on our own continent, the Lena and Yenissei in the Old World, and in all the rivers and lakes of the temperate zone, communicating with the Atlantic Ocean. They occur in smaller numbers in most tributaries of the Mediterranean, but are common in the Volga and Danube, as well as in the Mississippi, in some of the rivers on our northern Atlantic and Pacific coasts, and in China. This family has no representatives in Africa, Southern Asia, Australia, or South America, but there is a group corresponding in a certain way to it in South America,—that of the Goniodonts. Though some ichthyologists place them widely apart in their classifications, there is, on the whole, a striking resemblance between the Sturgeons and Goniodonts. Groups of this kind, reproducing certain features common to both, but differing by special structural modifications, are called ‘representative types.’ This name applies more especially to such groups when they are distributed over different parts of the world. To naturalists the comparison of one of these types with another is very interesting, as touching upon the question of origin of species. To those who believe that animals are derived from one another the alternative here presented is very clear: either one of these groups grew out of the other, or else they both had common ancestors which were neither Sturgeons nor Goniodonts, but combined the features of both and gave birth to each.

“There is a third family of fishes, the Hornpouts or Bullheads, called Siluroids by naturalists, which seem by their structural character to occupy an intermediate position between the Sturgeons and Goniodonts. There would seem to be, then, in these three groups, so similar in certain features, so distinct in others, the elements of a series. But while their structural relations suggest a common origin, their geographical distribution seems to exclude it. Take, for instance, the Hornpouts; they are very few in the northern hemisphere, hardly ever occurring in those rivers where the Sturgeons abound, and they are very numerous in the southern hemisphere, in southern Asia, Australia, Africa, and South America, where the Sturgeons are altogether wanting. In South America the Siluroids everywhere exist with the Goniodonts, in all other parts of the world without them; the Goniodonts being only found in South America. If these were the ancestors of the Siluroids in South America, they were certainly not their ancestors anywhere else. If the Sturgeons were the ancestors of the Siluroids and of the Goniodonts, it is strange that their progeny should consist of these two families in South America, and in the Old World of the Siluroids only. But if all three had some other common ancestry, it would be still more extraordinary that its progeny should exhibit so specific a distribution upon the surface of our globe. The Siluroids lay very large eggs, and as they are very abundant in South America we shall no doubt have opportunities of collecting them. Of the reproduction of the Goniodonts absolutely nothing is known. Of course the embryology of both these groups would have a direct bearing on the problem of their origin.

“Another family very abundant in various parts of the world is that of the Perches. They are found all over North America, Europe, and Northern Asia; but there is not one to be found in the fresh waters of the southern hemisphere. In South America and in Africa they are represented however by a very similar group, that of the Chromids. These two groups are so much akin that from their structure it would seem natural to suppose that the Chromids were transformed Perches; the more so, since in the western hemisphere the latter extend from the high north to Texas, south of which they are represented by the Chromids. Here the geographical as well as the structural transition would seem an easy one. But look at the eastern hemisphere. Perches abound in Asia, Europe, and Australia, but there are no Chromids there. How is it that the Perches of this continent have been so fertile in producing Chromids, and the Perches of all other continents, except Africa, absolutely sterile in this respect? Or if we reverse the proposition, and suppose the Perches to have grown out of the Chromids, why have their ancestry disappeared so completely on the Asiatic side of the world, while they do not seem to have diminished on this? And if Perches and Chromids should be represented as descending from an older common type, I would answer that Palæontology knows nothing of such a pedigree.

“Next come the Chubs, or in scientific nomenclature the Cyprinoids. These fishes, variously called Chubs, Suckers, or Carps, abound in all the fresh waters of the northern hemisphere. They are also numerous in the eastern part of the southern hemisphere, but have not a single representative in South America. As the Goniodonts are characteristic of the southern hemisphere in its western half, so this group seems to be characteristic of it in its eastern half. But while the Cyprinoids have no representative in South America, there is another group there, structurally akin to them, called the Cyprinodonts. They are all small-sized; our Minnows belong to this group. From Maine to Texas they are found in all the short rivers or creeks all along the coast. It is for this reason that I expect to find the short coast rivers of South America abounding in Minnows. I remember to have found in the neighborhood of Mobile no less than six new species in the course of an afternoon’s ramble. These fishes are almost all viviparous, or at least lay their eggs in a very advanced state of development of the young. The sexes differ so greatly in appearance that they have sometimes been described as distinct species, nay, even as distinct genera.[12] We must be on our guard against a similar mistake. Here again we have two groups, the Cyprinoids and Cyprinodonts, so similar in their structural features that the development of one out of the other naturally suggests itself. But in South America there are no Cyprinoids at all, while the Cyprinodonts abound; in Europe, Asia, and North America on the contrary, the Cyprinoids are very numerous and the Cyprinodonts comparatively few.” The Characines were next considered with reference to their affinities as well as their geographical distribution; and a few remarks were added upon the smaller families known to have representatives in the fresh waters of South America, such as the Erythrinoids, the Gymnotines, &c. “I am often asked what is my chief aim in this expedition to South America? No doubt in a general way it is to collect materials for future study. But the conviction which draws me irresistibly, is that the combination of animals on this continent, where the faunæ are so characteristic and so distinct from all others, will give me the means of showing that the transmutation theory is wholly without foundation in facts.” The lecture closed with some account of the Salmonidæ, found all over the northern hemisphere, but represented in South America by the Characines, distinct species of which may be looked for in the separate water-basins of Brazil; and also of several other important families of South American fishes, especially the Osteoglossum, the Sudis, &c., interesting on account of their relation to an extinct fossil type, that of the Cœlacanths.[13]

_April 17th._—Yesterday was Easter Sunday, and the day was beautiful. The services from Bishop Potter in the morning were very interesting; the more so for us on account of the God speed he gave us. Wind and weather permitting, it is the last Sunday we shall pass on board ship together. The Bishop spoke with much earnestness and sympathy of the objects of the expedition, addressing himself especially to the young men, not only with reference to their duties as connected with a scientific undertaking, but as American citizens in a foreign country at this time of war and misapprehension.

This morning we were quite entertained at meeting a number of the so-called “Catamarans,” the crazy crafts of the fishermen, who appear to be amphibious animals on this coast. Their boats consist of a few logs lashed together, over which the water breaks at every moment without apparently disturbing the occupants in the least. They fish, walk about, sit, lie down or stand, eat, drink, and sleep, to all appearance as contented and comfortable as we are in our princely steamer. Usually they go into port at nightfall, but are occasionally driven out to sea by the wind, and may sometimes be met with two hundred miles and more from the shore. To-day we have fairly come upon the South American coast. Yesterday we could catch sight occasionally of low sand banks; but this morning we have sailed past the pretty little town of Olinda, with its convent on the hill, and the larger city of Pernambuco, whose white houses come quite down to the sea-shore. Immediately in front of the town lies the reef, which runs southward along the coast for a hundred miles and more, enclosing between itself and the shore a strip of quiet waters, forming admirable anchorage for small shipping. Before Pernambuco this channel is quite deep, and directly in front of the town there is a break in the reef forming a natural gateway through which large vessels can enter. We have now left the town behind, but the shore is still in sight; a flat coast rising into low hills behind, and here and there dotted with villages and fishing-huts.

The lecture on Saturday was rather practical than scientific, on the best modes of collecting and preserving specimens, the instruments to be used, &c. To-day it was upon the classification of fishes as illustrated by embryology; the same method of study as that explained the other day and now applied to the class of fishes. “All fishes at the time when the germ becomes distinct above the yolk have a continuous fin over the whole back, around the tail, and under the abdomen. The naked reptiles, those which have no scales, such as frogs, toads, salamanders, and the like, share in this embryological feature of the fishes. From this identity of development I believe the naked reptiles to be structurally nearer to the true fishes than to the scaly reptiles. All fishes, and indeed all Vertebrates, even the highest, have, at this early period, fissures in the side of the neck. These are the first indications of gills, an organ the basis for which exists in all Vertebrates at a certain period of their life, but is fully developed and functionally active only in the lower ones, in which it acquires a special final structure; giving place to lungs in the higher ones before they reach their adult condition. From this time forward not only the class characters, but those of the family, begin to be distinguished. I will show you to-day how we may improve the classification of fishes by studying their embryology. Take, for instance, the family of Cods in its widest acceptation. It consists of several genera, among which are the Cod proper, the Cusk, and the Brotula. Naturalists may differ in their estimation of the relative rank of these genera, and even with reference to their affinity, but the embryology of the Cod seems to me to give the natural scale. In its early condition the Cod has the continuous fin of the Brotula, next the dorsal and caudal fins become distinct, as in the Cusk, and lastly the final individualization of the fins takes place, and they break up into the three dorsals and two anals of the Cod. Thus the Brotula represents the infantile condition of the Cod, and of course stands lowest, while the Cusk has its natural position between the two. There are other genera belonging to this family, as, for instance, the Lota or fresh-water Cusk and the Hake, the relative position of which may be determined by further embryological studies. I had an opportunity of observing something in the development of the Hake which throws some light on the relation of the Ophidini to the Cod family, though thus far they have been associated with the Eel. The little embryonic Hake on which I made my investigation was about an inch and a half in length; it was much more slender and elongated in proportion to its thickness than any of the family of Cods in their adult condition, and had a continuous fin all around the body. Although the structural relations of the Eels are not fully understood, some of them, at least, now united as a distinct family under the name of Ophidini, are known to be closely connected with the Cods, and this character of the Hake in its early condition would seem to show that this type of Eel is a sort of embryonic form of the Cod family.

“Another well-known family of fishes is that of the Lophioides. To this group belongs the Lophius or Goose-fish, with which the Cottoids or Sculpins, and the Blennioids, with Zoarces and Anarrhichas, the so-called Sea-cat, ought to be associated. It was my good fortune to have an opportunity of studying the development of the Lophius, and to my surprise I found that its embryonic phases included the whole series here alluded to, thus presenting another of those natural scales on which I hope all our scientific classifications will be remodelled when we obtain a better knowledge of embryology. The Lophius in its youngest stage recalls the Tænioids, being long and compressed; next it resembles the Blennioids, and growing stouter passes through a stage like Cottus, before it assumes the depressed form of Lophius. In the family of Cyprinodonts I have observed the young of Fundulus. They are destitute of ventrals, thus showing that the genus Orestias stands lowest in its family. I would allude to one other fact of this kind observed by Professor Wyman. There has been a doubt among naturalists as to the relative standing of the Skates and Sharks. On geological evidence I had placed the Skates highest, because the Sharks precede them in time; but this fact had not been established on embryological evidence. Professor Wyman has followed the embryology of the Skate through all its phases, and has found that in its earlier condition it is slender in outline, with the appearance of a diminutive shark, and that only later it assumes the broad shield-like form and long tapering tail of the skate. Were it only that they enable us to set aside all arbitrary decisions and base our classifications on the teachings of nature, these investigations would be invaluable; but their importance is increased by the consideration that we are thus gradually led to recognize the true affinities which bind all organized beings into one great system.”

_April 20th._—The day after to-morrow we shall enter the Bay of Rio de Janeiro. One begins to see already that little disturbance in the regularity of sea life which precedes arrival. People are making up their letters, and rearranging their luggage; there is a slight stir pervading our small party of passengers and breaking up the even tenor of the uniform life we have been leading together for the last three weeks. It has been a delightful voyage, and yet, under the most charming circumstances, life at sea is a poor exchange for life on land, and we are all glad to be near our haven.

On Tuesday the lecture was upon the formation and growth of the egg; a sort of practical lesson in the study of embryology; yesterday, upon the importance of ascertaining, at the outset, the spawning season of the animals in Brazil, and the means to that end. “It will often be impossible for us to learn the breeding season of animals, a matter in which country people are generally very ignorant. But when we cannot obtain it from persons about us, there are some indications in the animals themselves which may serve as a guide. During my own investigations upon the development of the turtles, when I opened many thousands of eggs, I found that in these animals, at least, the appearance of the ovaries is a pretty good guide. They always contain several sets of eggs. Those which will be laid this year are the largest; those of the following year are next in size; those of two years hence still smaller, until we come to eggs so small that it is impossible to perceive any difference between their various phases of development. But we can readily tell whether there are any eggs so advanced as to be near laying, and distinguish between the brood of the year and those which are to be hatched later. When the eggs are about to be laid the whole surface is covered with ramifying blood-vessels, and the yolk is of a very clear bright yellow. Before the egg drops from the ovary this network bursts; it shrivels up and forms a little scar on the side of the ovary. Should we, therefore, on examining the ovary of a turtle, find that these scars are fresh, we may infer that the season for laying is not over; or if we find some of the eggs much larger than the rest and nearly mature, we shall know that it is about to begin. How far this will hold good with respect to alligators and other animals I do not know. I have learned to recognize these signs in the turtles from my long study of their embryology. With fishes it could hardly be possible to distinguish the different sets of eggs because they lay such numbers, and they are all so small. But if we cannot distinguish the eggs of the different years, it will be something to learn the size of their broods, which differs very greatly in different families.”

The lecture concluded with some advice as to observing and recording the metamorphoses of insects. “Though much has been written on the societies of ants and other like communities in Brazil, the accounts of different naturalists do not agree. It would be well to collect the larvæ of a great many insects, and try to raise them; but as this will be difficult and often impossible in travelling, we must at least get the nests of ants, bees, wasps, and the like, in order to ascertain all we can respecting their communities. When these are not too large it is easy to secure them by slipping a bag over them, thus taking the whole settlement captive. It may then be preserved by dipping into alcohol, and examined at leisure, so as to ascertain the number and nature of the individuals contained in it, and learn something at least of their habits. Nor let us neglect the domestic establishments of spiders. There is an immense variety of spiders in South America, and a great difference in their webs. It would be well to preserve these on sheets of paper, to make drawings of them, and examine their threads microscopically.”

_April 21st._—Yesterday Mr. Agassiz gave his closing lecture, knowing that to-day all would be occupied with preparations for landing. He gave a little history of Steenstrup and Sars, and showed the influence their embryological investigations have had in reforming classification, and also their direct bearing upon the question of the origin of species. To these investigators science owes the discovery of the so-called “alternate generations,” in which the Hydroid, either by budding or by the breaking up of its own body, gives rise to numerous jelly-fishes; these lay eggs which produce Hydroids again, and the Hydroids renew the process as before.[14]

“These results are but recently added to the annals of science, and are not yet very extensively known in the community; but when the facts are more fully understood, they cannot fail to affect the fundamental principles of zoölogy. I have been astonished to see how little weight Darwin himself gives to this series of transformations; he hardly alludes to it, and yet it has a very direct bearing on his theory, since it shows that, however great the divergence from the starting-point in any process of development, it ever returns to the road of its normal destiny; the cycle may be wide, but the boundaries are as impassable as if it were narrower. However these processes of development may approach, or even cross each other, they never end in making any living being different from the one which gave it birth, though in reaching that point it may pass through phases resembling other animals.

“In considering these questions we should remember how slight are most of those specific differences, the origin of which gives rise to so much controversy, in comparison with the cycle of changes undergone by every individual in the course of its development. There are numerous genera, including many very closely allied species, distinguished by differences which, were it not for the fact that they have remained unchanged and invariable through ages, might be termed insignificant. Such, for instance, are the various species of corals found in the everglades of Florida, where they lived and died ages ago, and had the identical specific differences by which we distinguish their successors in the present Florida reefs. The whole science of zoölogy in its present condition is based upon the fact that these slight differences are maintained generation after generation. And yet every individual on such a coral stock,—and the same is true of any individual in any class whatsoever of the whole animal kingdom, whether Radiate, Mollusk, Articulate, or Vertebrate,—before reaching its adult condition and assuming the permanent characters which distinguish it from other species, and have never been known to vary, passes in a comparatively short period through an extraordinary transformation, the successive phases of which differ far more from each other than do the adult species. In other words, the same individual differs more from himself in successive stages of his growth than he does in his adult condition from kindred species of the same genus. The conclusion seems inevitable, that, if the slight differences which distinguish species were not inherent, and if the phases through which every individual has to pass were not the appointed means to reach that end, themselves invariable, there would be ever-recurring deviations from the normal types. Every naturalist knows that this is not the case. All the deviations known to us are monstrosities, and the occurrence of these, under disturbing influences, are to my mind only additional evidence of the fixity of species. The extreme deviations obtained in domesticity are secured, as is well known, at the expense of the typical characters, and end usually in the production of sterile individuals. All such facts seem to show that so-called varieties or breeds, far from indicating the beginning of new types, or the initiating of incipient species, only point out the range of flexibility in types which in their essence are invariable.

“In the discussion of the development theory in its present form, a great deal is said of the imperfection of the geological record. But it seems to me that, however fragmentary our knowledge of geology, its incompleteness does not invalidate certain important points in the evidence. It is well known that the crust of our earth is divided into a number of layers, all of which contain the remains of distinct populations. These different sets of inhabitants who have possessed the earth at successive periods have each a character of their own. The transmutation theory insists that they owe their origin to gradual transformations, and are not, therefore, the result of distinct creative acts. All agree, however, that we arrive at a lower stratum where no trace of life is to be found. Place it where we will: suppose that we are mistaken in thinking that we have reached the beginning of life with the lowest Cambrian deposit; suppose that the first animals preceded this epoch, and that there was an earlier epoch, to be called the Laurentian system, beside many others older still; it is nevertheless true that geology brings us down to a level at which the character of the earth’s crust made organic life impossible. At this point, wherever we place it, the origin of animals by development was impossible, because they had no ancestors. This is the true starting-point, and until we have some facts to prove that the power, whatever it was, which originated the first animals has ceased to act, I see no reason for referring the origin of life to any other cause. I grant that we have no such evidence of an active creative power as Science requires for positive demonstration of her laws, and that we cannot explain the processes which lie at the origin of life. But if the facts are insufficient on our side, they are absolutely wanting on the other. We cannot certainly consider the development theory proved, because a few naturalists think it plausible: it seems plausible only to the few, and it is demonstrated by none. I bring this subject before you now, not to urge upon you this or that theory, strong as my own convictions are. I wish only to warn you, not against the development theory itself, but against the looseness in the methods of study upon which it is based. Whatever be your ultimate opinions on this subject, let them rest on facts and not on arguments, however plausible. This is not a question to be argued, it is one to be investigated.

“As I have advanced in these talks with you, I have become more and more dissatisfied, feeling the difficulty of laying out our work without a practical familiarity with the objects themselves. But this is the inevitable position of one who is seeking the truth: till we have found it, we are more or less feeling our way. I am aware that in my lectures I have covered a far wider range of subjects than we can handle, even if every man do his very best; if we accomplish one tenth of the work I have suggested, I shall be more than satisfied with the result of the expedition. In closing, I can hardly add anything to the impressive admonitions of Bishop Potter in his parting words to us last Sunday, for which I thank him in your name and my own. But I would remind you, that, while America has recovered her political independence, while we all have that confidence in our institutions which makes us secure, that so far as we are true to them, doing what we do conscientiously and in full view of our responsibilities we shall be in the right path, we have not yet achieved our intellectual independence. There is a disposition in this country to refer all literary and scientific matters to European tribunals; to accept a man because he has obtained the award of societies abroad. An American author is often better satisfied if he publish his book in England than at home. In my opinion, every man who publishes his work on the other side of the water deprives his country of so much intellectual capital to which she has a right. Publish your results at home, and let Europe discover whether they are worth reading. Not until you are faithful to your citizenship in your intellectual as well as your political life, will you be truly upright and worthy students of nature.”

At the conclusion of these remarks a set of resolutions was read by Bishop Potter.[15] They were followed by a few little friendly speeches, all made in the most informal and cordial spirit; and so ended our course of lectures on board the Colorado. Later in the day we observed singular bright red patches in the sea. Some were not less than seven or eight feet in length, rather oblong, and the whole mass looked as red as blood. Sometimes they seemed to lie on the very top of the water, sometimes to be a little below it, so as only to tinge the rippling surface. One of the sailors succeeded in catching a portion of it in a bucket, when it was found to consist of a solid mass of little crustaceans, bright red in color. They were all very lively, keeping up a constant rapid motion. Mr. Agassiz examined them under the microscope and found them to be the young of a crab. He has no doubt that every such patch is a single brood, floating thus compactly together like spawn.

Footnote 2:

On the 17th of May, nearly a month after our arrival in Rio, this cloud was interpreted to us. It was, indeed, charged with the issues of life and death, for it was on this day and the following that the final assaults on Petersburg were made, and the cloud which marred an otherwise stainless sky, as we were passing along the shores of Virginia, was, no doubt, the mass of smoke gathered above the opposing lines of the two armies.

Footnote 3:

The species of Hydroids most numerous upon the gulf-weed have not yet been described, and would form a valuable addition to the Natural History of the Acalephs. For an account of the animals of this class inhabiting the Atlantic coast of North America, and especially the New England shores, I may refer to the third volume of my Contributions to the Natural History of the United States, and to the second number of the Illustrated Catalogue of the Museum of Comparative Zoloögy at Cambridge.—L. A.

Footnote 4:

“This stream,” he writes, “is probably generated by the great accumulation of water on the eastern coast of America, between the tropics, by the trade-winds which constantly blow there.” These views, though vaguely hinted at by old Spanish navigators, were first distinctly set forth by Franklin, and, as is stated in a recent printed report of the Coast Survey Explorations, “they receive confirmation from every discovery which the advance of scientific research brings to aid in the solution of the great problem of oceanic circulation.”

Footnote 5:

No one can read the account of the explorations undertaken by the Coast Survey in the Gulf Stream, and continued during a number of successive years, and the instructions received by the officers thus employed from the Superintendent, Dr. A. D. Bache, without feeling how comprehensive, keen, and persevering was the intellect which has long presided over this department of our public works. The result is a very thorough survey of the stream, especially along the coast of our own continent, with sections giving the temperature to a great depth, the relations of the cold and warm streaks, the form of the ocean bottom, as well as various other details respecting the direction and force of the current, the density and color of the water, and the animal and vegetable productions contained in it. (See Appendix No. I.)—L. A.

Footnote 6:

This anticipation was more than confirmed by the result of the journey. It is true that Mr. Agassiz did not go beyond the Peruvian frontier, and therefore could not verify his prophecy in that region. But he found the localization of species in the Amazons circumscribed within much narrower limits than he expected, the whole length of the great stream, as well as its tributaries, being broken up into numerous distinct faunæ. There can be no doubt that what is true for nearly three thousand miles of its course is true also for the head-waters of the Amazons; indeed, other investigators have already described some species from its higher tributaries differing entirely from those collected upon this expedition.

Footnote 7:

Mr. Agassiz afterward visited these hills himself, and an account of their structure and probable origin will be found in the chapter on the physical history of the Amazons.

Footnote 8:

See Appendix No. II.

Footnote 9:

It proved in the sequel unnecessary to seek the glacial phenomena of tropical South America in its highest mountains. In Brazil the moraines are as distinct and as well preserved in some of the coast ranges on the Atlantic side, not more than twelve or fifteen hundred feet high, as in any glaciated localities known to geologists in more northern parts of the world. The snow line, even in those latitudes, then descended so low that masses of ice formed above its level actually forced their way down to the sea-coast.—L. A.

Footnote 10:

In copying the journal from which these notes are taken, I have hesitated to burden the narrative with anatomical details. But for those who take an interest in such investigations it may be well to add here that the frog, when first hatched, is simply an oblong body, without any appendages, and tapering slightly towards its posterior end. In that condition it resembles the Cecilia. In its next stage, that of the tadpole, when the extremity has elongated into a tail, the gills are fairly developed, and it has one pair of imperfect legs, it resembles the Siren, with its rudimentary limbs. In its succeeding stages, when the same animal has two pairs of legs and a fin around the tail, it recalls the Proteus and Menobranchus. Finally the gills are suppressed, the animal breathes through lungs, but the tail still remains; it then recalls Menopoma and the Salamanders. At last the tail shrinks and disappears, and the frog is complete. This gives us a standard by which the relative position of the leading groups of the class may safely be determined.—L. A.

Footnote 11:

On account of the many exploring expeditions for which the Bay of Rio de Janeiro has been a favorite port, it has acquired a special interest for the naturalist. It may seem at first sight as if the fact that French, English, German, Russian, and American expeditions have followed each other in this locality, during the last century, each bringing away its rich harvest of specimens, by diminishing its novelty would rather lessen than increase its interest as a collecting ground. On the contrary, for the very reason that the specimens from which the greater part of the descriptions and figures contained in the published accounts of these voyages were obtained from Rio de Janeiro and its neighborhood, it becomes indispensable that every zoölogical museum aiming at scientific accuracy and completeness should have original specimens from that very locality for the identification of species already described. Otherwise doubts respecting the strict identity or specific difference of specimens obtained on other parts of the Atlantic shore, not only in South America but in Central and North America, may at any time invalidate important generalizations concerning the distribution of animals in these seas. From this point of view, the Bay of Rio de Janeiro forms a most important centre of comparison, and it was for this reason that we made so prolonged a stay there. Although the prospect of discovering any novelties was diminished by the extensive investigations of our predecessors, I well knew that whatever we collected there would greatly increase the value of our collections elsewhere. One of my special aims was to ascertain how far the marine animals inhabiting the coast of Brazil to the south of Cape Frio differed from those to the north of it, and furthermore, how the animals found along the coast between Cape Frio and Cape St. Roque differed from or agreed with those inhabiting the more northern shore of the continent and the West Indian Islands. In the course of the following chapters I shall have occasion to return, more in detail, to this subject.—L. A.

Footnote 12:

Molinesia and Pœcilia.

Footnote 13:

This lecture was accompanied by careful descriptions and drawings on the blackboard, showing the structural differences between these groups. These are omitted, as they would have little interest for the general reader. The chief object in reporting these lectures is to show the aims which Mr. Agassiz placed before himself and his companions in laying out the work of the expedition, and these are made sufficiently clear without further scientific details.

Footnote 14:

As these investigations have been published with so much detail (Steenstrup, Alternate Generation, Sars’s Fauna Norwegica; L. Agassiz, Contr. to Nat. Hist. of U. S.), it has not been thought necessary to reproduce this part of the lecture here. Any one who cares to read a less technical account of these investigations than those originally published, will find it in “Methods of Study,” by L. Agassiz.

Footnote 15:

See Appendix No. III.