Part 11

Contemplating now the ants as in some respects an excluded race, which with a large share of pugnacity can not find a basis of operations for contending against the bees, we have to turn attention briefly on their modes of life. The industry of the ant is proverbial, and can not fail to arrest the attention of any one who spends a few minutes before an ant-hill. But carefully recorded observations prove it to be much greater than could have been imagined. Sir John Lubbock has rendered special service here by carefully noting the time occupied, as well as the amount of work done, thus preserving a series of observations exceedingly suggestive in many ways, and having an important bearing on a considerable number of difficult questions connected with the relative powers of lower and higher orders of life. A similar service has been rendered in America in the work of the Rev. H. C. McCook of Philadelphia, on _The Natural History of the Agricultural Ant of Texas_,--a book recording careful and most important observations, adding much to the stores of knowledge concerning ants.[CH]

The work of the ants is directed mainly to the two great objects of animal life, procuring food, and caring for the young, to which falls to be added, the repelling of attacks upon their nests, or removal of any thing obnoxious. They destroy great numbers of smaller insects, bearing them to their nests for consumption, besides going off in search of honey which may be within reach, and not guarded with spikes. This mode of providing implies a very busy life, and they do not as a rule grudge work. Besides procuring supplies, however, there is a large amount of labor in the care bestowed upon their young. Without attempting to distinguish various orders, of which "more than seven hundred kinds are known,"[CI] a general description of their young will suffice. In the earliest stage of their existence, the larvæ are small conical shaped grubs, without power of movement. In this state they are fed, carried about from place to place as if their seniors were seeking change of air and temperature for them; and in process of these removals and arrangements, they are often grouped together in separate companies, and in exact order according to their size. In their next stage, they become pupæ, sometimes quite exposed, in other cases covered with a thin silken covering. From this, they pass into the mature state as perfect insects, and in process of this transition older ants render assistance by way of aiding the transition, "carefully unfolding their legs and smoothing out their wings."

In the ant nest there is a singular distinction of orders which prevents us speaking of the _parent_ ants as doing all this work for the young. The great majority in every nest are neuters, not producing young; these are the workers, and they are destitute of wings. The smaller numbers only are the males and females producing the young. The workers, shorn of wings, and entrusted with all that is required in household and out-door duties, labor assiduously. These neuter ants have occasioned special perplexity to Mr. Darwin as bearing on the theory of evolution, a difficulty which is seriously increased by the fact that in some cases they "differ from each other, sometimes to an almost incredible degree, and are thus divided into two or even three castes," and these "do not commonly graduate into each other," but are "as distinct from each other as any two species."[CJ] Without following Mr. Darwin through his reasoning as to the adaptation of neuters for their task in life, it may be well to quote his words towards its close, where he says, "I must confess, that, with all my faith in natural selection, I should never have anticipated that this principle could have been efficient in so high a degree, had not the case of these neuter insects led me to this conclusion."[CK] Besides the fact that these neuters are the workers, there is an additional circumstance, established by Mr. Frederick Smith by observations in England, confirmed by the observations of Pierre Huber in Switzerland, and afterwards verified in the clearest way by Mr. Darwin, that there is a species of ant (_formica sanguinea_) which captures slaves of a weaker order, making war against the weaker race, carrying off their young, rearing them within their own nests, and training them to serve. Mr. Darwin was himself sceptical of such a statement, but gives an interesting narrative of distinct observations by which it was confirmed.

The amount of labor undertaken by the workers from an ants' nest, may be judged by one or two extracts from the records of Sir John Lubbock. He says, "I once watched an ant from six in the morning, and she worked without intermission till a quarter to ten at night," and in that time she had carried one hundred and eighty-seven larvæ into the nest.[CL] There is evidence not only of coöperation, but of division of labor among the workers. The observations of Mr. Forel lead to the conclusion that "very young ants devote themselves at first to the care of the larvæ and pupæ, and that they do not take share in the defence of the nest or other out-of-door work, until they are some days old."[CM] By a distinct set of observations, watching all ants that came and went from the nest, and laying up in captivity some of the number, Mr. Lubbock came to the conclusion "that certain ants are told off as foragers."[CN] And in the winter season, when in the case of some orders little food is required, a few only of the inhabitants of the nest come and go, for the purpose of carrying in supplies. This makes observation much more easy at that season, rendering it possible to number and identify individual workers. The results as applicable to one of the nests are given in the following sentences. "From the 1st of November to the 5th of January, with two or three casual exceptions, the whole of the supplies were carried in by three ants, one of whom, however, did comparatively little. The other two were imprisoned, and then, but not till then, a fresh ant appeared on the scene. She carried in the food for a week, and then she being imprisoned, two others undertook the task."[CO]

One consideration more bearing upon obtaining supplies deserves to be recorded as altogether singular. Some species of ants watch over a distinct order of insects, the aphides, which exude a sweet fluid, using them exactly as we do cows for obtaining supplies of milk. The ant comes up to the aphis, gently strokes it with her feelers, forthwith the aphis gives forth its supply of honey, which the ant drinks up and departs. The facts were observed by Pierre Huber, and verified by Mr. Darwin. This verification was so interesting, that I give the narrative in a slightly condensed form. Mr. Darwin says,--"I removed all the ants from a group of about a dozen aphides on a dock-plant, and prevented their attendance during several hours." Mr. Darwin tried in vain by stroking the aphides with a hair, in imitation of the play of the feelers of the ants, to induce them to give up the honey. "Afterwards," he says, "I allowed an ant to visit them, and it immediately seemed, by its eager way of running about, to be well aware what a rich flock it had discovered; it then began to play with its antennæ on the abdomen first of one aphis and then of another; and each, as soon as it felt the antennæ, immediately lifted up its abdomen and excreted a limpid drop of sweet juice, which was eagerly devoured by the ant."[CP] So the ants have their "cows" and milk them.

To attempt any account of the ants of tropical countries, where ants are most numerous, swarming in the regions they inhabit, and marching in hosts, would occupy too much space. I give, therefore, only a single reference extracted from the testimony of Mr. Savage concerning the driver ant of Western Africa (_Anomma Arcens_), so called because of the success with which it drives every thing before it. Mr. Savage annoyed by the proximity of a large settlement, discovered its quarters in some decaying granite. Kindling a fire around it, he believed he had succeeded in disposing of that settlement. Two days after, he went back to the spot, and instead of desolation and death, he found "a tree at a short distance, about eighteen inches in diameter, to the height of four feet from the ground, with the adjacent plants and earth perfectly black with them." The most striking thing, however, was that the ants had made festoons from the lower branches to the ground, formed in the following manner, as witnessed by Mr. Savage: "ant after ant coming down from above, extending their long limbs, and opening wide their jaws, gradually lengthening out the living chain" until first it was swaying to and fro, and ultimately fastened to the ground, when "others were ascending and descending upon them, thus holding free and ready communication with the lower and upper portions of this dense mass." In this same manner these ants provide for the crossing of water when on the march. "They make a line or chain of one another, gradually extending themselves by numbers across till the opposite side is reached."[CQ] This is exactly similar to the manner in which some monkeys are known to construct a natural bridge, only that the monkeys have the advantage of greater size and muscular strength, as well as prehensile power by the use of their tails. With such characteristics as have been briefly described, there is little wonder that a high place in the scale of intelligence has been claimed for these small insects. Sir John Lubbock, who has so patiently conducted his observations as to their modes of life, has stated this in the following manner,--"The anthropoid apes no doubt approach more to man in bodily structure than do any other animals; but when we consider the habits of ants, their social organization, their large communities, elaborate habitations, their roadways, their possession of domestic animals, and even in some cases of slaves, it must be admitted that they have a fair claim to rank next to man in the scale of intelligence."[CR] Whether, even with all this evidence, we may be able to rank the ants quite as high as Lubbock here suggests, may be open to question. There may, for example, be reasonable debate whether the dog does not present still higher signs of intelligence, but it says a great deal for the ants that debate in the case should be possible. A question of very great scientific importance is here raised, affecting the whole scheme of interpretation applicable to animal life, as connected with development of brain.

Without attempting to enter upon the argument yet to be conducted through the wider relations concerned, it must be obvious that the facts bearing on insect life must erelong have a larger share than they have yet had in influencing our generalizations. By reference to these, it becomes apparent, that anatomical structure is not in itself an adequate guide in determining comparative importance on the scale of organic existence; and, what is still more startling, that even comparative brain structure can not be taken as the sole test of the measure of intelligence belonging to animals. The whole orders of ants, taken collectively, must be regarded as presenting quite exceptional difficulties, not only for a theory of evolution regarded as an all-embracing science of life; but also for that theory of intelligence which seeks to account for diversities of power by the comparative complexity of brain structure.

Passing from more detailed discussion, it is needful to observe how wide and valuable are the results of these researches concerning the relation of the vegetable kingdom with lower orders of animals. Facts now recorded in multitudes of scientific journals, and more elaborate treatises, illustrate wonderful minuteness of contrivance and completeness of adaptation in the works of nature, giving to the range of knowledge possessed only a century ago an aspect of insignificance. What the microscope has done by enlarging the range of human vision, subdivision of labor among scientific inquirers, and proportionate concentration, have done, in the way of embracing the vast and complicated field, of observation lying open to all eyes. The results exalt to a greatly higher place in our appreciation the evidence of design in the world. The consequence is that while the line of thought followed by Paley, in what he designated _Natural Theology_, has become a thousand-fold more interesting, the familiar and now almost antiquated illustration of the _watch_, taken as a model of human design, by the comparative simplicity of its adjustments, seems strangely inadequate to represent even in the most temporary form, a minuteness of design quite overwhelming to the human mind in its attempts to bring it within a uniform scheme. Whether all this was provided for by manifold creative acts, or by development from a few primordial forms, does not affect the argument; the latter suggestion only greatly increases its force. To those who are swayed only by an intellectual interest, the facts of vegetable and insect life must be full of significance, suggestive of far-reaching reflection. But to no body of men can these results of scientific research be so attractive as to those who require for all nature a supernatural explanation.

FOOTNOTES:

[BR] _Lay Sermons_, chap, vii., p. 134.

[BS] Darwin's _Fertilization of Orchids_, p. 2; Lubbock's _Scientific Lectures_, p. 8.

[BT] Sir John Lubbock's _Scientific Lectures_, p. 3. Mr. Darwin refers to Fritz Müller's papers as reported in _Botanische Zeitung_, 1869-70. Appendix IX.

[BU] _The Various Contrivances by which Orchids are fertilized by Insects_, 2d ed. p. 293.

[BV] _Fertilization_, p. 5.

[BW] _Fertilization_, p. 12.

[BX] _Fertilization_, p. 102.

[BY] _Ib._ p. 113.

[BZ] _Fertilization_, p. 44.

[CA] _Scientific Lectures_, p. 31.

[CB] _Fertilization_, p. 2.

[CC] _Ib._ p. 284.

[CD] _Fertilization_, p. 285.

[CE] _Fertilization_, p. 246.

[CF] _Botany_, (Science Primers) by Dr. J. D. Hooker, C.B., P.R.S., p. 79.

[CG] _Scientific Lectures_, p. 36.

[CH] See Appendix X.

[CI] See Appendix VIII.

[CJ] _Origin of Species_, 6th ed. p. 230.

[CK] _Origin of Species_, 6th ed. p. 233.

[CL] _Scient. Lects._ p. 73.

[CM] _Ib._ p. 78.

[CN] _Ib._ p. 135.

[CO] _Scientific Lectures_, p. 135.

[CP] _Origin of Species_ 6th ed. p. 207.

[CQ] _Museum of Natural History_ edited by Richardson, Dallas, Cobbold, Baird, and White, vol. ii. p. 184.

[CR] _Scient. Lects._ p. 68.

LECTURE VI.

HIGHER ORGANISMS.--RESEMBLANCES AND CONTRASTS.--BRAIN STRUCTURE.

The stage of investigation now reached requires us to consider recent advances in our knowledge of more complicated organisms. This leads into the line of observation disclosing steadily advancing complexity of structure, and brings us into contact with the claim that man be included within the area of scientific inquiry, and regarded as a more fully organized life to which lower orders are not only pointing, but actually tending.

As to this last claim, about which more must be said as we approach the close of these investigations, it may be remarked by way of preliminary, that as man belongs to nature, all the characteristics of his life must come within the area of scientific inquiry, and indeed the test of any theory of existence which may be offered, will be found in the measure of success with which it explains our own nature. That man stands highest in the scale of organism belonging to this world admits of no doubt, therefore the explanation of human nature may be regarded as the supreme effort of science. Around this subject, however, serious differences have arisen among scientific men, but these differences do not concern the very simple question whether all that belongs to nature comes within the range of the science of nature. This is granted by all, whether there be a preference for including all such inquiry under the single name of science, or for distinguishing between physical science and mental philosophy. This is simply a matter of defining terms, and tracing the boundaries of recognized departments of inquiry. But whether a continued study of organism will conduct us to an adequate understanding of human nature, must be a matter of observation and inference. If it do, science has completed its work. If it do not, there remains a still higher question, how shall we account for features of life for which organism affords no scientific explanation? The whole field is certainly free to science, and the whole task which this immense field of research imposes must be undertaken, and persistently prosecuted to a rational issue.

Entering now, therefore, on the contemplation of animal life, regarded as a higher order, distinguishable from vegetable life, we have the outstanding characteristics of sensibility and locomotion. Whether there is a distinct line of demarcation between vegetable and animal does not require special attention, for no matter of controversy on this point can delay procedure. There is, as already remarked, in the vegetable kingdom a singular approximation towards animal life, in so far as we have evidence of sensibility to touch among the plants, to a degree which appears wonderful chiefly by contrast with the common characteristics of the vegetable kingdom.

On the other hand, sensibility to influences operating from without is a common feature of animal life. Even the very lowest orders of animals are sensitive to touch, and as this form of experience is closely connected with power of locomotion, all animals have the conditions of their life largely affected by interference with their own movements, or resistance offered, whether by objects lying in their way, or by some force restraining their progress, or causing movement in an opposite direction. Now these two characteristics--sensibility to impression from without, and movement caused by an exercise of energy from within the organism itself--are both provided for by means of the nerve system belonging to the animal. This nerve system varies in the number and complexity of its arrangements, according to the complexity of the organism with which it is associated. As, therefore, we rise in the scale, passing from the soft pulpy form of the lowest orders, to those formed in segments or rings, next to those with distinct portions of organism fulfilling separate functions, as in insect life, with head, body, and legs; and next pass up to the vertebrates, with back-bone and skeleton, on which is built up a more or less complicated muscular system, we find a nerve system, growing in complexity along with the appearance of different organs of the body. And in all cases, this system fulfils these two functions--sensibility to touch, and movement of the body. These two are provided for by distinct lines or nerve fibres; and in all cases, these two sets are combined in a centre, thereby securing that the two sets be coöperative, unitedly contributing to the management of the living organism. This appears even if we take for illustration an organism so low as the _ascidian mollusk_, which floats in the water as if it were a sack drawn together towards the top, bulging out below; and which is nourished simply by the passing of a current of water in at the mouth, and out at a vent towards the lower end of the sac. A series of nerve lines comes from the mouth; a distinct ramification spreads over the lower portion of the sac; and these two are united in a single knot or ganglion, a little above the vent. By these contrivances, this little body, though for the most part stationary, is sensitive to the approach of any thing injurious, and by contraction of its mass expels the water with considerable force, driving the injurious matter to a distance. This combination of the two sets of nerves appears more strikingly in such an animal as the _centipede_, along whose body are successive groups of nerves, combined in regular order in a series of knots, and united longitudinally by connecting threads, attaching the successive knots. The same plan is carried up into a more articulated form in the case of the _winged insect_, with head, antennæ or feelers projecting from the head, wings, and legs, leading to a more marked appearance of separate combinations, giving greater prominence to the head. When from this we rise to the _fish_, thence to the _bird,_ thence to the _quadruped_, we find the head made conspicuously the central organ of the entire nerve system of the animal, while it occupies the front position in the body. It is no longer one of a set or series of knots; nor even the largest or more conspicuous in a graduated order of centres; but in the head of the animal is found that which is the true nerve centre for the whole nerve system, designated the brain. In the case of the vertebrates, not only does the skeleton afford the solid frame-work on which the muscular system is built, but the back-bone contains within it the main column of nerve fibres, which are given out at the several joints according to the requirements of the body.

If meanwhile we concentrate attention on our own bodies, we may by the aid of personal experience find easy illustration of the prominent features of the nerve system. We shall take first the _two distinct lines_ of nerves already mentioned, the one set concerned with sensibility, the other with movement of the muscles. From the tips of the fingers there run lines of nerve fibre, which are brought into combination at the wrist, and are carried up the arm, and onward by the shoulder and upper portion of the back-bone to the head. These are the nerves of _sensibility_, by means of which, as by telegraph wires, the slightest impression made on the tips of the fingers is instantly conveyed to the great nerve centre in the brain. Distinct from these is another set of nerves issuing from the brain, and descending the arm, giving off its fibres as it passes to the several muscles above the elbow, next to those above the wrist, and next to the muscles of the hand and fingers. These are the nerves of _movement_, by means of which the whole arm may be brought into action at pleasure, or the hand may be set to work, while the arm is at rest.