Part 9

I have not found the slightest difficulty in capturing Amblyopsis with a small dip net, either from a boat or while wading through the subterranean stream, and I have caught one in the hollow of my hand. At such a time all the noise I could make did not affect the fishes found swimming in the water. Frequently they were taken in the dip net without apparently noting the vibrations produced in the water until they were lifted out of it; very rarely a fish became evidently scared. Such a one would dart off a few feet or a few inches, and remain on the _qui vive_. If not pursued, it soon swam off quietly; if pursued, it not infrequently escaped by rapidly darting this way and that; when jumping out of the water, often an abrupt turn in the opposite direction from which it started would land it in the net, showing that their sense of direction was not very acute. At other times, if disturbed by the waves produced by wading, one or another individual would follow a ledge of rock to the bottom of the stream, where it would hide in a crevice. But very frequently, much more frequently than not, no attention was paid either to the commotion produced by the wading or by the boat and dip net. In general, it may be said that the fishes in their natural habitat are oblivious to disturbances of the water until frightened by some very unusual jar or motion, probably a touch with the net, when they become intensely alert. The fact that they are not easily frightened suggests the absence of many enemies, while their frantic behavior if once scared gives evidence either that occasional enemies are present and that they are very dangerous, or that the transmission of the instinct of fear is as tenacious as the transmission of physical characters.

Contrary to Sloan’s observation, that they detect the presence of a solid substance in their path, I have never noticed that those in confinement became aware of the proximity of the walls of the aquarium when swimming toward it. Instead, they constantly use the padded, projecting lower jaw as bumpers. Even an extremely rapid dart through the water seems to be stopped without serious inconvenience by the projecting jaw.

The first observations on the feeding habit of Amblyopsis are those of Cope. He remarks that “the projecting lower jaw and upward direction of the mouth render it easy for the fish to feed at the surface of the water, where it must obtain much of its food.... This structure also probably explains the facts of its being the sole representative of the fishes in subterranean waters. No doubt many other forms were carried into the caverns since the waters first found their way there, but most of them were like those of our present rivers--deep-water or bottom feeders. Such fishes would starve in a cave river, where much of the food is carried to them on the surface of the stream.”

The observations of Cope are entirely erroneous, as we shall see, and the speculations based on them naturally fall to the ground.

Dr. Sloan recorded one Amblyopsis which he kept twenty months without food. “Some of them would strike eagerly at any small body thrown in the water near them, rarely missed it, and in a very short time ejected it from their mouths with considerable force. I tried to feed them often with bits of meat and fish-worms, but they retained nothing. On one occasion I missed a small one, and found his tail projecting from the mouth of a larger one.”

Wyman found a small-eyed fish in the stomach of an Amblyopsis.

Hoppin was struck by the fact that, if not capable of long fasts, Troglichthys must live on very small organisms that the unaided eye can not discern. Garman found, in the stomachs of Troglichthys collected by Hoppin in Missouri, species of Asellus, Cambarus, Ceuthophilus, and Crangonyx.

All the specimens of Amblyopsis so far taken by me contained very large fatty bodies in their abdominal cavity, a condition suggesting abundance of food. The stomachs always contained the _débris_ of crustaceans, a closer identification of which was not attempted. One young Amblyopsis disappeared on the way home from the caves, and had evidently been swallowed by one of the larger ones. A few old ones, kept in an aquarium from May to July, were seen voiding excrement toward the last of their captivity, and their actions at various times suggested that they were scraping the minute organisms from the side of the aquarium. The young Amblyopsis reared in the aquarium seemed to feed on the minute forms found in the mud at the bottom of its aquarium. Some Cœcidotæa placed in the aquarium of the young soon disappeared, and the capture of one of these was noted under a reading glass. The fish was quietly swimming along the side of its aquarium; when it came within about an inch of the crustacean it became alert, and with the next move of the Cœcidotæa it was captured with a very quick, well-aimed dart on the part of the young fish. Others were captured while crawling along the floor of the aquarium. From all things noted, it seems very probable that Amblyopsis is a bottom feeder, and that it also picks food from the walls of the caves. It is not at all improbable or impossible that food should be captured at the surface or in open water, but there seems no warrant for Cope’s supposition that Amblyopsis is a top feeder. I have frequently seen larger specimens, which had been in captivity for several weeks, nosing about the bottom of the aquarium, with their bodies inclined upward in the water and quietly taking in the organic fragments at the bottom. An Asellus stirring about at such a time always produced an unusual alertness.

The number of respiratory movements of Amblyopsis averaged nineteen a minute in five observations, reaching a maximum of thirty in a small individual and a minimum of fourteen in a large one. This is in strong contrast to Chologaster, the number of whose respiratory motions reached an average of eighty per minute in five observations, with a minimum of fifty-six and a maximum of one hundred and eight in a small specimen. Dr. Loeb has called my attention to the more rapid absorption of oxygen in the light than in the dark; this extended would probably mean the more rapid absorption of oxygen through the skin of light-colored animals, a matter of doubtful value, however, to species living in the dark.

The gill filaments are small as compared with the gill cavity.

Oxygenation probably takes place through the skin. Ritter[J] has suggested the same for Typhlogobius.

[J] Ritter, Museum of Comparative Zoölogy, vol. xxiv, p. 92.

“Cutaneous respiration is not unique in Typhlogobius and the Amblyopsidæ. In the viviparous fishes of California the general surface, and especially the fins, which have become enormously enlarged, serve as respiratory organs during the middle and later periods of gestation; the fins are a mass of blood-vessels, with merely sufficient cellular substance to knit them together. There is, however, no pink coloration.”

Skin respiration would account for the extreme resistance to asphyxiation in Amblyopsis and Typhlogobius. About forty-five examples of Amblyopsis were carried in a pail of water four hundred miles by rail, with only a partial change of water three times during twenty-four hours. A smaller number may be kept for days or weeks--probably indefinitely--in a pail of water without change. The characteristics of Typhlogobius along this line have been set forth elsewhere.

Sticks, straws, etc., are never avoided by the fishes even when perfectly imperturbed. By this I mean that they are never seen to avoid such an object when it is in their path. They swim against it and then turn. An object falling through the water does not disturb them, even if it falls on them. A pencil gently moved about in front of them does not disturb the fishes much, but if the pencil is held firmly in the hand it is always perceived, and the fish comes to a dead halt ten or fifteen millimetres before it reaches such an object. On the other hand, they may be touched on the back or tail before they start away. They glide by each other leisurely and dignified, and if they collide, as they sometimes do, they usually show no more emotion than when they run against a stick. But this indifference is not always displayed, as we shall see under the head of breeding habits.

A number kept in an aquarium with a median partition, in which there was a small opening, were readily able to perceive the opening, swimming directly for it when opposite it. This observation is in direct contrast to their inability to perceive solid substances in their path. A sharp tap on the sides of an aquarium in which six blind fishes were swimming, where they had been for a number of days undisturbed, in a dark room, caused nearly all of them to dart rapidly forward. A second tap produced a less unanimous reaction. This repeated on successive days always brought responses from some of the inmates of the aquarium. Those responding were not necessarily the nearest to the center of disturbance, but sometimes at the opposite side of the aquarium or variously distributed through it. After a few days the fishes took no notice of the tapping by any action observable in the artificially lighted room.

Such tapping on a well-lighted aquarium containing both Chologaster and Amblyopsis was always perceived by the Amblyopsis, but the only response from these imperturbable philosophers was a slight motion of the pectorals, a motion that suggested that their balance had been disturbed and that the motion was a rebalancing. Chologaster, on the other hand, invariably darted about in a frantic manner. One individual of Amblyopsis floating on the water was repeatedly pushed down by the finger without being disturbed. If, however, they are touched on the side they always rapidly dart away.

From everything observed, it is quite evident that Amblyopsis is not keener in perceiving objects or vibrations than other fishes, and ordinarily pays much less attention to them. Whether it possesses a greater power of discrimination of vibrations it would be difficult to say. It certainly possesses very elaborate tactile organs about the head. These tactile organs are probably more serviceable in detecting and precisely locating prey in the immediate neighborhood than for anything else. Some observations on young Amblyopsis are of interest in this connection.

The young, with a large amount of yolk still attached, show a well-developed sense of direction. A needle thrust into the water near their heads and in front of them causes a quick reaction, the young fishes turning and swimming in the opposite direction. They will do this two or three times, then, becoming exhausted, will remain at rest. Sometimes an individual will not move until it is actually touched by the needle. The needle must come within about three or four millimetres of the fish before it is noticed. Then, if it produces any result, it causes the fish to quickly turn and swim some distance, when it falls to the bottom again and remains at rest. If the needle is placed behind the fish, it will swim directly forward; if at the side or about the middle, it causes the fish to swim directly forward or to turn and swim in a direction opposite the origin of the disturbance. Younger specimens have, as yet, no power over the direction of their progress; the wiggling of the tail simply produces a gyration, with the yolk as pivot.

A young blind fish, six months old, swims about in a jerky manner, chiefly by the use of its pectoral fins. It keeps close to the side of the vessel, usually with its back to the glass. (The aquarium was a cylindrical jar three hundred millimetres in diameter and three hundred millimetres high.) It perceives a stick thrust toward it as readily as a seeing fish can. It always perceives from whatever direction it may be approached, and will invariably dart away a short distance, sometimes making sharp turns to avoid the stick, and always successfully. It can be approached from the top nearer than from the sides or from in front. It does not avoid the sides of the aquarium, which it frequently strikes. It is a bottom feeder; its intestinal canal is always partially full.

A long series of experiments was made on Amblyopsis and Chologaster to determine their reaction to white and monochromatic light. Without going into the details of these experiments, it may be stated that Amblyopsis avoids the light, regardless of the direction or the color of the rays. The same is true of Chologaster, except that they were positively attracted by the red rays of the spectrum as against the blue.

We owe the first observations on the breeding habits of Amblyopsis to Thompson, who states that a fish “was put in water as soon as captured, where it gave birth to nearly twenty young, which swam about for some time, but soon died; ... they were each four lines in length.” Little or nothing has been added to our knowledge of this subject since that time, but the highly interesting supposition of Thompson that they were viviparous has gained currency, and it is therefore unfortunate that in this respect he was in error.

Putnam adds to the above that, judging from some data in his possession, the young are born in September and October, and further along remarks that they are “undoubtedly” viviparous.

The eggs are laid by the female in under her gill membrane. Here they remain for perhaps two months, till the yolk is nearly all absorbed. If a female with young in her gill pouches is handled, some of the young are sure to escape. This was observed, and gave rise to the idea that this fish is viviparous. Eggs have been obtained as early as March 11th and as late as September, and the indications are that the breeding season extends throughout the year. The eggs are large--2.3 millimetres in diameter from membrane to membrane--and about sixty to seventy are laid at one time.

Certain structures gain an entirely new significance in the light of the breeding habits. These are the enlarged gill cavities, with the small gills, the closely applied branchiostegal membrane, and the position of the anus and sexual orifices. The latter are placed just behind the gill membrane in such close proximity to it that they can be covered by it. It is probable, therefore, that the membrane is drawn over the sexual orifice and the eggs deposited directly into the gill cavity. In an individual thirty-five millimetres long the anus is situated between the origin of the pectorals; in one twenty-five millimetres long it lies between the pectorals and ventrals. In the young it lies behind the ventrals, as in other fishes.

In an aquarium containing six Amblyopsis two took a great antipathy to each other. Whenever they touched, a vigorous contest began. Frequently they came to have a position with broadside to broadside, their heads pointing in opposite directions. At such a time the fight consists in quick lateral thrusts toward the antagonist to seize him with the mouth. The motion is instantly parried by a similar move by the antagonist. This blind punching may be kept up for a few seconds, when, by their vigorous motions, they lose each other and jerk themselves through the water from side to side, apparently hunting for each other. At this time they are very agile, and move with precision. When the belligerents meet one above the other, the snapping and punching is of a different order. While jerking through the water immediately after a round, if one of the belligerents touches one of the neutrals in the aquarium it frequently gives it a punch, but does not follow it up, and the unoffending fellow makes haste to get out of the road, the smaller ones doing so most quickly. If, after an interval of a few seconds, a belligerent meets a neutral they quietly pass each other without paying any further attention, whereas if the two belligerents meet again there is an immediate response. Whether they recognize each other by touch or by their mutual excitability I do not know. At one time, in another aquarium, I saw one belligerent capture the other by the pectorals. After holding on for a short time it let go, and all differences were forgotten. The thrust is delivered by a single vigorous flip of the tail and caudal to one side. These fights were frequently noticed, and always occurred between males.

The absence of secondary sexual differences in the cave fishes is a forcible argument in favor of sexual selection as the factor producing high coloration in the males. The absence of secondary sexual differences in cave animals opposes the idea of Geddes and Thompson that the differences are the external expression of maleness and femaleness.

Attempts at acclimating Amblyopsis in outside waters have so far failed.[K] A few were placed in Turkey Lake, Indiana. They were surrounded by a fine wire net, to keep off other fishes. They died in a few days, as the result of attacks of leeches, _saprolegnia_, or fish mold, and from unknown causes. Others were kept in an elongated box sunk into the ground, where fresh spring water flowed through it constantly. _Saprolegnia_ sooner or later destroyed all of them. They live longest in quiet aquaria, where the water is rarely changed. The young I have secured died, with one exception, within a few weeks. The difficulty of rearing the young is not at all insurmountable. They eat readily. Their aquaria must be kept free from green plants, and have a layer of fine mud, with a few decaying leaves, in the bottom. They will feed on minute crustaceans and other micro-organisms. When they have reached a sufficient size, examples of Asellus are greedily devoured. Fish mold is the bane of the larvæ. Many of them were found with tufts of the _hyphæ_ growing out of their mouths and gill openings.

[K] Since the above was written an apparently successful attempt has been made to colonize them in a pool at Winona Lake. A record of this colony will be published later.

THE MAN OF SCIENCE IN PRACTICAL AFFAIRS.

BY F. W. CLARKE.

The human mind is addicted to the creation of types, a process which implies classification and generalization of a somewhat low order. Some prominent feature of the thing classified is selected for emphasis, and there is often a degree of exaggeration which leads, in the end, to caricature. John Bull, Brother Jonathan, the Jew of the comic papers, and the stage Irishman are examples of this tendency. So, too, a profession or occupation is summed up in one conventional character, with a little truth distorted as if seen reflected from the surface of a curved mirror. The likeness is there, but unlike the reality. The individual embodiment of the type is rarely, if ever, encountered.

The man of science deals with questions which commonly lie outside of the range of ordinary experience, which often have no immediately discernible relation to the affairs of everyday life, and which concentrate the mind upon apparent abstractions to an extraordinary degree. Accordingly, the scholar, the scientific investigator, is typified as an elderly dreamer in spectacles, who is so uncouth, so self-forgetful, so absent-minded, and so ignorant of practical matters as to be hardly more than a child. He is one to be cared for and humored, like an imbecile--treated with some consideration, perhaps, on account of his learning, but never to be trusted in the transaction of business nor in the administration of public affairs. With him, as an antithesis, is contrasted the practical man, who knows whither his steps are tending, who has learned to control others, and who never dreams of abstractions during office hours, if indeed he troubles himself about them at all. The one is thought to be vague, visionary, and unpractical; the other is deemed efficient, precise, prompt, and clear. Has this distinction any basis in reality? Do scientific pursuits disqualify a man for administrative responsibility?

These questions, like all other legitimate questions, are to be answered by evidence, and the popular impression is entitled to no weight whatever. This evidence is to be found by a study of the thing itself, the man of science as he actually is; by an examination of the training which he receives, the character of the work which he does, and the results which he accomplishes. By this method it will be found that the supposed type is purely imaginary, that the workers in science exhibit all the variations which are found in any other group of occupations, that the human race as a whole is their only symbol or representative. The man of science may be grave or gay, moral or immoral, social or unsocial, keen or visionary--in short, he may exemplify any trait of human nature, except the traits of ignorance and stupidity. He must be intelligent and educated, methodical and exact; apart from these qualifications he may resemble any other man, chosen from any other vocation. Indeed, his nearest analogue is the so-called man of business, and the chief distinction between the two is that one deals with unfamiliar, the other with familiar things.

The direct tendency of the scientific training is to develop as fully as possible the positive traits which have been mentioned. Each science is a body of systematic, well-organized knowledge, with clear fundamental principles and distinct outlines. The study of science is a continual discouragement of obscurity or vagueness; it is a discipline in the statement and solution of definite problems, and it trains one to see things as they are, apart from all irrelevancies. The technicalities of science, so bewildering to the layman, are merely aids to exactness, avoidances of circumlocution--in short, they are practical devices whereby labor is saved. Economy of effort is one of the features in which the scientific training excels.