The Zoologist/4th series, vol 5 (1901)/Issue 723/Biological Suggestions. Animal Sense Perceptions, Distant

by William Lucas Distant

 

THE ZOOLOGIST

 

---

 

No. 723.—September, 1901.

 

---

 

BIOLOGICAL SUGGESTIONS.

ANIMAL SENSE PERCEPTIONS.

By W. L. Distant.

 

Whether Bees are susceptible of feeling and capable of thought is a question which cannot be dogmatically answered.—Huxley.

It is indeed still not infrequently the custom to deny absolutely to the lower animals reason and religion.—Haeckel.

It is, I think, generally assumed not only that the world really exists as we see it, but that it appears to other animals pretty much as it does to us. A little consideration, however, is sufficient to show that this is very far from being certain, or even probable.—Lord Avebury (Sir John Lubbock).

Underlying all our conceptions of Animal Mimicry and Protective Resemblance is the predicate that other animals see the various objects of nature in similar size, shape, and colour as we do ourselves; in other words, that, though the sensory organs of sight may vary, the practical result is still identical. The same remark applies in a general way to a belief in a more or less universal and similar sensation of touch, smell, taste, and hearing, though on examination it is surprising to find how little positive information exists to warrant the conclusion, even though it may be an absolute fact. If Berkeley asked the old materialistic philosophers whether they could prove the existence of a material world external to the mind, may we not also ask for some more definite proof of the unity and similarity in the sense perception of animals? If Teufelsdröckh reduced society to a theory of clothes, it would seem that many advocates of Mimicry represent nature by a theory of masks. We observe a strong similarity between an animal and its environment, or between one which we believe possesses a quality procuring immunity from attack, and another in which that quality is absent, and we conclude that the resemblance or mimicry is equally observable by other creatures. Surely an element of error is present in this deduction. Is our world as we see it—and thus can only imagine it—the same in actual identity as that known by the sense cognitions of all animal life? If, as has been ably remarked, the universe contained only blind and deaf beings, it is impossible for us to imagine but that darkness and silence should reign everywhere.^[1] If, on the other hand, we allow—as surely we ought—variation to exist in sense perceptions, as it undoubtedly does in the structure of sense organs, then, without leaving this planet, we may well understand that there are "other worlds than ours." Even in homology and variation, as Bateson has observed, "we have allowed ourselves to judge too much by human criterions of difficulty, and we have let ourselves fancy that nature has produced the forms of life from each other in the ways which we would have used, if we had been asked to do it."^[2] Our knowledge of the sense organs in the lower animals is still very imperfect, and sometimes erroneous. Thus Weismann, in his lecture on the "Retrogressive Development in Nature," delivered in 1866, refers to the "Cæcilians, tropical worm-like or snake-like Amphibians, living underground," as having "lost not only the sense of sight, but that of hearing also." When this lecture was translated and published in this country a few years later, the author added a footnote, that "Recent researches have shown us that these animals not only possess a complete auditory apparatus, but that it is even more perfect than in other Amphibia"; and he adds, as a justification for the statement on which he founded his former conclusions, that "Up to the present time our knowledge of the auditory organ of Cæcilia has been founded upon the statements of two excellent observers, Professors Retzius and Wiedersheim; but the material at their disposal was restricted to a few badly preserved specimens."^[3] The importance of a clear comprehension of animal sense cognitions when a theory like that of mimicry is propounded must be obvious. Take, for instance, a bird and a protectively coloured caterpillar, such as it appears to our cognitions. Should the power of vision in the bird be in excess of that possessed by ourselves, the resemblance may be only superficial and powerless; should it be less, then the protection may be excessive—an idea almost unthinkable in the light of the doctrine of natural selection. We may see what appears to be, and may be, wonderful assimilative colouration or mimicking disguise, but the creature so protected, as it appears to us, may be readily detected by a keenness of scent in its enemies, of which we know little, or by a power of hearing, of which we know less. We certainly do not hear a tithe of the sounds produced by insects; the effect of some stridulating organs we can only comparatively estimate by their structural affinities to others of a more developed character, and which produce sounds capable of being recognized by our own sense of hearing. It is probable that many insect enemies discover their prey by sound alone.^[4] Other creatures find their food without apparently either sight or hearing. According to Jonathan Couch, the common Sea-hog or Sea-egg (Echinus esculenius), "though apparently destitute of every sense, or possibility of regarding external objects by sight or hearing,^[5] will travel up the rods of a crab-pot, enter the opening, descend within, mount again to the situation of the bait, and select the particular one that pleases it best."^[6] The homing habits of the Common Limpet (Patella vulgata) have been ascribed to the possession of a "locality sense."^[7]

Nearly all writers and investigators have felt the difficulty in properly describing the sensory impressions of animal life. According to Prince Kropotkin:—"We must be prepared to find that the usual division of senses into touch, taste, smell, vision, and hearing will not do for the whole series. The senses must be rather divided into a mechanical, chemical, temperature, and light sense, to which the electrical sense will perhaps have to be added. Such a division undoubtedly better answers to the senses which exist in the lower animals, and when the series is considered in an ascending order, the gradual differentiation of the chemical sense into taste and smell, and of the mechanical sense into touch, hearing, and pressure sense, becomes evident."^[8] Brehm states that careful observations on the habits of Mosquitos "places it beyond doubt that in the discovery of their victim they are guided less by sight than by smell, or perhaps, more correctly, by a sense which unites smell and tactile sensitiveness;^[9] while Mr. J.A. Thomson, in an editorial note, remarks: "The somewhat mysterious reference which Brehm makes to a sense between smell and touch is thoroughly justifiable. To the senses of many of the lower animals—and even of fishes—it is exceedingly difficult to apply our fairly definite human conceptions of smell, taste, touch, &c."^[10] The restlessness or alarm shown by birds or other animals before the occurrence of an earthquake sensible to man is well known, and is probably due to the very small tremors which precede the larger vibrations.^[11] Dr. Alexander Hill has recently sympathetically approached this subject, and we give one extract in his own words:—"If we try to figure to ourselves the mental activities of any animal, we recognize at once that its thought must take the colour of the sense by which they are chiefly prompted. A Dog, for example, does not recognize 'a family likeness,' but a family smell. In a day of happy wandering down the village street, and through the lanes, it pays no attention to the picturesque. As it lies in front of the fire, reviewing the experiences of the day, it recalls a long succession of suggestive smells. It is the cheek-bristles of the Otter which vibrate with excitement as it remembers the slipperysided Salmon it nearly mistook for an alder-root. The Cat twitches its ears as it dreams of bursting unannounced into a seminary of Mice. If we wish in any degree to realize what our thoughts would be like if we were to exchange our brain for the brain of some other animal, we must ask, first. Which of the five sense organs is the one through which this particular animal chiefly looks out upon the world?"^[12] Again:—"We see with the clearness of the lower vertebrates—birds, reptiles, and fishes, in which vision is mono-scopic—although we, in common with Monkeys, and some other of the higher vertebrates, have acquired the power of stereoscopic vision."^[13] Jordan and Kellogg, in a recent volume in which the theory of mimicry is treated as an absolute fact, still remark:—"It will be recognized that in the study of how other animals feel and taste and smell and hear and see, we shall have to base all our study on our own experience. We know of hearing and seeing only by what we know of our own hearing and seeing; but by examination of the structure of the hearing and seeing organs of certain other animals, and by observation and experiments, zoologists are convinced that some animals hear sounds that we cannot hear, and some see colours that we cannot see."^[14] If we consider the lives of purely nocturnal animals, the fact is impressed on our minds with irresistible force, that the world they see and know must have a totally different aspect to what we realize by the light of day, whilst their living environment is also under different conditions. Except on moonlight nights darkness must reign supreme, whilst a general silence replaces the hum of animal life, and nature ever seems to sleep. Such must be the experience of an animal like the Tasmanian Devil (Sarcophilus ursinus). The Common Earthworm must possess little cognition of a material world external to its very limited sense perceptions. As remarked by Darwin:—"Worms are poorly provided with sense organs, for they cannot be said to see, although they can just distinguish between light and darkness: they are completely deaf, and only have a feeble power of smell: the sense of touch alone is well developed."^[15] The world as we know it is therefore actually non-existent to these simply organised animals.

The microscope reveals the existence of living beings of which by our unaided eyesight we should have scarcely dreamed; or, if the scientific imagination had been compelled to predicate their being to account for physical and evolutionary results, we should still have been in profound ignorance as to their structure, life, or habits.^[16] So we may readily imagine some animals as possessing a sense of vision unfolding the details of nature around us in a manner far beyond our ken, while others may have the sensations of sight so blunted and obtuse that only the mighty things of the world come under their individual notice. If we allow our reason to run riot with the first reflection, we can conceive a sky and earth very dissimilar to those of our experience. Through an atmosphere clouded with dust and germs such beings should gaze upon a sun by day as only known at present by our telescopes; at night the story told by astronomers would be exhibited to their unaided eyes: all ideas of dimension would be increased; the hidden things of natural life would be exposed; animal and vegetable tissues would appear transformed, and our ideas as to assimilation in colour and structure be in many cases destroyed, and others created of a fuller and more comprehensive type. Under the second supposition the mystery of life would be still more behind the veil than at present, natural causation would be even less understood; things would be fewer and farther away, the smaller non-existent, the larger more superficially appreciated. Would nature be the same under such different conceptions?—and yet the sense of sight has been alone considered. With a difference in the sensory organs or sensations of smell, a fetid stink might be appreciated as a sweet odour; touch may from a similar reason become an unknown and unimagined power, or an imperfectly realized sensation; from a like cause taste may be so varied as to be outside the nauseous or agreeable experiences; while the sense of hearing might develop a familiarity with sounds of which we are absolutely ignorant, or otherwise prove oblivious to some of our most common perceptions.^[17] Without losing ourselves in metaphysical subtleties as to whether things really exist as cognizable by our sense organs, or whether much of our materialism is not only to a considerable degree a question of sensation, we must at least push that problem beyond ourselves, and estimate it throughout all animal life if we hope to gain any clear ideas of the phenomena of animal colouration, or the more complex conceptions of mimicry or protective resemblance. For instance, it has been proposed that the striped Tiger finds the protection of "aggressive mimicry" by the blending of its colours, or the assimilation of the same, with the reeds or bamboo clusters in which it hides. This is undoubtedly true so far as our own sense organs or powers of sight are concerned; but do the Antelopes or other animals on which it preys have the same sensations on the matter as ourselves? Increase the penetrating power of vision, and the differences will be so clearly seen and magnified that the theory falls to the ground; decrease the same, and the proposition becomes more capable of proof. And yet this is the crucial question; one we answer by inferences, but one to which we can give no absolute reply.

Again, what do we know as to the colour perceptions of insects?^[18] From experiments made with Ants, Lord Avebury considers as proved that these insects perceive the ultra-violet rays. As he remarks:—"As every ray of homogeneous light which we can perceive at all appears to us as a distinct colour, it becomes probable that these ultra-violet rays must make themselves apparent to the Ants as a distinct and separate colour (of which we can form no idea), but as unlike the rest as red is from yellow, or green from violet. The question also arises whether white light to these insects would differ from our white light in containing this additional colour. At any rate, as few of the colours in nature are pure, but almost all arise from the combination of rays of different wave-lengths, and as in such cases the visible resultant would be composed not only of the rays which we see, but of these and the ultra-violet, it would appear that the colours of objects and the general aspect of nature must present to them a very different appearance from what it does to us."^[19] The late Prof. Riley was of the same opinion:—"So far as experiments have gone, they show that insects have a keen colour sense, though here again their sensations of colour are different from those produced upon us."^[20] It is said that certain night-flying insects invariably visit white flowers, as we reasonably believe, because of the easy detection of that colour in an obscure light, and we may accept the night preference to such flowers as an undoubted fact.^[21] But we cannot say that the hue which we describe as white is the same as that apprehended by the insects. Distinct it must undoubtedly be to secure the permanent selection of their visits, but we can say no more. Because an insect invariably selects and visits a flower of one particular colour, we can only record the observation, but certainly not assume that what we see as white is seen by them in the same hue. Mr. J.A. Harvie-Brown has protested against the assumption "that the colour of insects, as seen by us, is comparable with what may be seen by fish. Fish see though a different medium from ours, and surely we see differently through theirs."^[22] Prof. Plateau, an authority on the physiology of Arthropods, a few years ago published a series of memoirs giving the results of his experiments in endeavouring to ascertain the actual powers of vision possessed by insects and other Arthropods.^[23] Dr. Sharp, of Cambridge, has placed us all under an obligation by giving a condensed account of these observations, and also a critical summary of results. He gives his general impressions as derived from Plateau's experiments as follows:—

"1. Insects in motion are guided largely by the direction of light, and the existence of lights and shades. That when walking they are guided by a combination of light-impressions, with specific habit (that is, going upwards or downwards, towards the light, or away from the light), and by tactile impressions; these latter not acting when the insect is in flight.

"2. That there is at present no evidence at all that the light perceptions are sufficiently complex to be entitled to be called seeing; but that, as the large development of the compound eye permits the simultaneous perception of movement, its direction, and of lights and shades over a certain area, a Dragonfly may pursue and capture another insect without seeing it in our sense of the word seeing."^[24]

Before leaving this section of our subject, and to make clear our suggestion that little can be justly predicated as to sight preferences or warnings by insects, we may again quote Mr. G. J. Storey, who describes the limits of insect vision, in the terms of a coarse mosaic or rough imperfect representation of the external world, the result of the perceptions acquired by their compound eyes; while he asserts that "the insect cannot see more details upon its own antennæ, close as they are to it, than we can with our own naked eye. We must therefore dismiss from our thoughts the mistaken impression that insects see very minute objects far beyond human vision."^[25] Nor can we, as remarked before, conclude that they appreciate colours similarly to ourselves. The question was well put by Lord Rayleigh some years ago, who added the remark:—"Surely this is a good deal to take for granted when it is known that even among ourselves colour-vision varies greatly, and that no inconsiderable number of persons exist to whom, for example, the red of the scarlet geranium is no bright colour at all, but almost a match with the leaves."^[26] The only rejoinder to this proposition at the time was the suggested argument based on the spectrum of the light of the Firefly, which had been found to be perfectly continuous, without traces of lines either bright or dark, and to extend from about the line C in the scarlet to F in the blue. It is composed of rays which act powerfully on the eye, but produce little thermal or actinic effect. In other words, the fly, in producing its light, wastes but little of its power. The writer, however, was careful to add:—"This, it is true, tells us nothing as to the colour sensations of the insect, but it appears to show that the same rays are luminous to its eyes which are luminous to ours."^[27] This is precisely the view here again suggested—the same ray or object is seen as by ourselves; but the colour, size, or structure of both respectively may be altogether different, or at least considerably diverse from those apprehended by our own cognitions. This does not, however, necessarily invalidate the conclusions we have formed as to the actual existence of some forms of protection by what we understand as mimicry or protective resemblance. It may be taken to prove that both the object resembled and the mimicking creature may possess the unison we see, but under different characters and under different conditions. Thus to a colour-blind person who visualizes blue as green, what we should understand as a wonderful resemblance in a blue animal to its blue environment would be to him the assimilation in colour of two green objects. To a near-sighted person,^[28] the mimicking resemblance of a Phasma to the leaf or twig on which it was found would probably be much greater than that appreciated by the possessor of stronger and more penetrating powers of vision; and the same fact as observed by both would, if analytically recorded in each case, be capable of modifying or enlarging our conceptions of the phenomena or theory under consideration. But how much more cogent is this suggestion if we compare the resultant of human power of vision with that possessed by other animals—say, as low in the scale of derivation as insects—whose eyes have a structure so dissimilar to our own, and whose sensory impressions are therefore likely to be so totally diverse.^[29] The very essence of the theory of evolution predicates a vast difference in the sensation of vision, which must vary as the organ does in structure. As Darwin observes:—"Within the highest division of the animal kingdom, namely, the Vertebrata, we can start from an eye so simple, that it consists, as in the Lancelet, of a little sack of transparent skin, furnished with a nerve, and lined with pigment, but destitute of any other apparatus. In fishes and reptiles, as Owen has remarked, 'the range of gradations of dioptric structures is very great.'"^[30] Wallace states his conviction that "long- and short-sightedness, and the various diseases and imperfections to which the eye is liable, may be looked upon as relics of the imperfect condition from which the eye has been raised by variation and natural selection."^[31]

Do we not therefore go far beyond the scientific use of the imagination, when, as in the practice now so much in vogue, we not only conclude that every well-established colour and marking, if not advantageous, is certainly not disadvantageous in the struggle for existence, but add the further postulate that they are so by reason that animal vision appreciates them in the same manner as understood by ourselves.

Even among ourselves the power of sight is a variable quantity. Hottentots have been described as possessing keen powers of vision. By the quickness of their eyes they can discover buck and other kinds of game from a great distance; "they are equally expert in watching a Bee to its nest. They no sooner hear the humming of the insect than they squat themselves on the ground, and, having caught it with the eye, follow it to an incredible distance."^[32] Lumholtz gives a similar testimony. "The Australian Bee is not so large as our House-fly, and deposits its honey in hollow trees, the hives sometimes being high up. While passing through the woods, the Blacks, whose eyes are very keen, can discover the little Bees in the clear air as the latter are flying thirty yards high to and from the little hole which leads into their store-house. When the natives ramble about in the woods they continually pay attention to the Bees, and when I met Blacks in the forests they were, as a rule, gazing up in the trees. Although my eyesight, according to the statement of an oculist, is twice as keen as that of a normal eye, it was usually impossible for me to discover the Bees, even after the Blacks had indicated to me where they were."^[33] Darwin has remarked, as a result of reviewing the evidence on the subject, that savages are generally long-sighted, and quotes Rengger's experience in Paraguay as to repeated observations that Europeans who had been brought up and spent their whole lives with the wild Indians did not equal them in the sharpness of their senses.^[34] On the other hand, as the result of the 'Report of the Anthropometric Committee, British Association, 1881,' Mr. Roberts stated that the figures gave no support to the belief that savages possess better sight than civilized peoples, and spoke of "the common mistake of travellers in confounding acuteness of vision with the results of special training or education of the faculty of seeing, results which," as he remarked, "are quite as much dependent on mental training as in the use of the eyes." As pointed out by Haeckel, our own eyes are subject to the law of divergent adaptation. "If, for example, a naturalist accustoms himself always to use one eye for the microscope... then that eye will acquire a power different from that of the other.... The one eye will become short-sighted, and better suited for seeing things near at hand; the other eye becomes, on the contrary, more long-sighted, more acute for looking at an object in the distance. If, on the other hand, the naturalist alternately uses both eyes for the microscope, he will not acquire the shortsightedness of the one eye, and the compensating degree of long sight in the other, which is attained by a wise distribution of these different functions of sight between the two eyes."^[35] And so, even at the risk of being accused of rank Lamarckism,^[36] may we not assume a similar process to have occurred with the eyes of insectivorous birds to whom a microscopic search for insects becomes a necessity of life; whilst the soaring Vulture has developed a long-sightedness which enables it, if not to see the quarry, at all events to discern its distant companion descending to the same. We have said we may be accused of Lamarckism, because it does not seem to be allowed by many of the followers of Weismann that an acquired character may be capable of being perpetuated and accentuated by the action of "Natural Selection."^[37]

As with insects, we know little of the sight perceptions of other and much more highly developed animals. When in South Africa, I kept a young Baboon, who seemed pleased, at the decline of day, to mount a low roof, and watch the setting sun. I gazed at the same, but did we both see a similar appearance?^[38] Turner could see and paint a sunset unappreciable by the senses of ordinary men who possess similar organs of sense. What did my Baboon see as he gazed in the same direction as myself? The question seems unanswerable. Could it have faithfully drawn and painted what it saw, such a picture could only appear to my senses as an exact representation of what I now see, and therefore believe to exist. The Baboon could only represent the phenomenon under the colours as they appeared to him, but if such colours have a different appearance to me, both picture and subject would still be identical, and prove absolutely nothing. To take an extreme illustration. Suppose what is white to me is black to my Baboon, and vice versâ. If my animal faithfully paints a white flower as black, as it sees it, the picture must still show a white flower to me, because of our different sense appreciations.^[39]

Leeches (Clepsine) afford a good instance of the variety in sense perception. Prof. Whitman has paid much attention to these animals, and writes:—"Pass the hand over a dish in which a number of Clepsines are resting quietly on the bottom, and at a distance of a few inches above the animals, taking care not to make the least jar or other disturbance. If the animals are quite hungry, the slight shadow of the hand, imperceptible though it be to our eyes, will be instantly recognized by them, and a lively scene will follow, every Leech rising up, supported on its posterior sucker, and swinging at full length back and forth, from side to side, round and round, as if intensely eager to reach something. Put a Turtle in the dish, and see what a scramble there will be for a bloody feast. The shadow of the hand was to these creatures like the shadow of a Turtle swimming or floating over them in their natural haunts, and hence their quick and characteristic response. A piece of board floating over them would have the same effect. Although so sensitive to a small difference in light, the Clepsine eyes can give no pictures, and hence there is no power of visual discrimination between objects. They probably recognize their right host by the aid of organs of taste, and at any rate they are often able to distinguish their host from closely allied species."^[40]

It is a long jump from a Leech to a Rhinoceros, but the principle is the same, though the animals in a developmental sense are so widely divided. Dr. Livingstone describes the Rhinoceros as having such dimness of vision as to make it charge past a man who has wounded it, if he stands perfectly still, in the belief that its enemy is a tree. Dr. Livingstone, however, adds that this imperfect sight probably arises from the horn being in the line of vision, "for the variety named Kuabaoba, which has a straight horn directed downwards away from that line, possesses acute eyesight, and is much more wary."^[41] Mr. Scott Elliot feels sure that the East African Rhinoceros cannot see clearly for more than about fifty yards.^[42] Mr. Blanford, writing on the Abyssinian Rhinoceros, states that "they are easily eluded by turning, as they are not quick of sight, and, like most mammals, they never look for enemies in trees; consequently a man two or three feet from the ground will remain unnoticed by them if he keeps quiet."^[43] Elephants are reported to have a most defective power of sight, and, generally speaking, among mammals, as a rule, the world, as known by their senses, is probably if we judge by vision alone, a much more circumscribed one than that cognized by ourselves. With other senses much more developed, and with the addition of some of which we are totally ignorant, nature may be to them revealed beyond our imagination.

According to Dr. Günther, fishes, in the range of their vision and acuteness of sight, are very inferior to the higher classes of vertebrates; yet, at the same time, it is evident that they perceive their prey or approaching danger for a considerable distance; and it would appear that the visual powers of a Periophthalmus, when hunting insects on mud-flats of the tropical coasts, are quite equal to those of a Frog.^[44] The Norwegian fishermen whitewash the rocks in the vicinity of their nets, or, where there are no rocks, erect white boards, or suspend sheets, which are termed "Salmon attractors," designed to represent the foam of the cataract, which the Salmon is seeking to ascend. But while the white colour is found attractive, the fishermen believe that the fish avoids red colours, so that red clothing is carefully discarded; and, according to Bishop Pontoppidan, even red tiles have been removed for this reason from a fisherman's house.^[45] Dr. S. Dixon, a president of the Pennsylvania Academy of Natural Sciences, in Philadelphia, had a large aquarium containing goldfish and other aquatic creatures, which he was in the habit of feeding every morning. During the winter, according to the 'New York Tribune,' he wore dark coloured clothing, and as soon as he approached the glass tank all the fish came to the surface of the water looking for crumbs. Changing his clothes to light-coloured fabrics the first day of May, the fish failed to recognize him, and went without food for two days. In fact, we cannot always conclude that the possession of eyes in some fishes is an indication of sight. According to Mr. Beddard, many deep-sea animals are totally blind; yet many species found in the deepest hollows of the ocean appear to have perfectly normal eyes. These discrepancies were partly accounted for by the theory of abyssal light. The histological study of the eyes of certain deep-sea Isopoda, particularly of Serolis and Arcturus, shows, however, that the appearance of well-developed eyes was often deceptive. Anyone, before having recourse to the microtome, would assert that the deep-sea Serolis neæva^[46] was as keen-eyed as any species of the genus. Yet sections through the eyes show that it is in a condition of degeneration; apart from the faceted cornea, there is but little of recognizable eye-structure left. In S. bromleyana the eyes are well-marked, but entirely devoid of pigment; no trace of optic tissue could be found by microscopical investigation. Mr. Beddard is therefore of opinion that there is no need of any theory of abyssal light; it is more likely that the state of preservation of the eyes is an index of the length of time that the species in question has been an inhabitant of the deeper waters.^[47] The sight perception of fishes is clearly a phenomenon, of which we have practically the smallest information, and the scantiest imagination.

It is even probable, as Bernstein has proposed, that the perception of the external world is essentially an act of the mind, which has its seat in the cerebrum, and is connected with this organ; and, further, that the sensory organ, with its nervous connections, only affords the brain the material which it converts into a Sensory Perception.^[48] For it has been observed with Pigeons, that upon the removal of the cerebral hemispheres, in which state they may live for some time, they still possess a sensation of light, which penetrates the eye, and causes a contraction of the pupil; an action which can only be caused by the central organ of the optic nerve in the brain. But a comprehension of the objects seen—i.e. a true perception of the senses—is no longer possible to these animals. They behave like blind animals, run against every obstacle, and no longer possess the power of recognizing the objects seen as belonging to the external world.^[49]

If it is granted that the perception of the external world is essentially an act of the mind, and has its seat in the cerebrum of man, and that Pigeons are proved to have the same relation between their sight perceptions and the integrity of their cerebral hemispheres, then we cannot hesitate to apply the qualifying influence of difference in evolution of cerebral matter between man and other animals as largely modifying their power of equally appreciating by sight the shape, colour, and size of the different natural objects around them. We may therefore pause before concluding that the insectivorous mammal, bird, or reptile sees as we do the "protective" or "non-protective" shape and colouration of its prey, or that the bird to the insect, or the insect to the bird, appears to each, as both to ourselves. And so with all that we consider "warning colours," a great element of error may exist in our calculations, owing to a difference in the sense perceptions of the animals most clearly interested in the theory formulated.

 

(To be continued.)

 

---

1. Huxley, 'Collected Essays,' vol. vi. p. 253.
2. 'Materials for the Study of Variation,' p. 33.
3. 'Essays upon Heredity, &c.' Eng. transl. vol. ii. p. 9.
4. "It is of course possible, if not probable, that Ants, even if deaf to sounds which we hear, may hear others to which we are deaf" (Lord Avebury (Sir John Lubbock), 'Ants, Bees, and Wasps,' p. 223).—"There are sounds which we cannot hear, there are sights which the eye cannot see. But besides all these there must be countless aspects of external nature of which we have no knowledge; of which, owing to the absence of appropriate organs, we can form no conception; which imagination cannot picture, nor language express" (Balfour, 'Foundations of Belief,' p. 69).—On the other hand, Mr. Pocock asserts that "there is not a particle of evidence that either the large Spiders or the Scorpions can hear the sounds that their own stridulating organs emit" ('Natural Science,' vol. ix. p. 24).—Mr. Edmund Selous inclines to the view that "thought transference" occurs among birds ('Bird Watching,' p. 219 et seq.).
5. By experiment, Romanes found "the Echini manifesting a strong disposition to crawl towards, and remain in, the light" ('Jelly-Fish, Star-Fish, and Sea-Urchins,' p. 319).
6. 'Illustrations of Instinct,' p. 12.
7. Cf. Lloyd Morgan and J.R.A. Davis, 'Nature,' Dec. 6th, 1894, and March 28th, 1895.
8. 'Nineteenth Century,' vol. xl. p. 252.
9. 'From North Pole to Equator,' p. 84.
10. Ibid. p. 568.
11. Cf. 'Nature,' vol. liv. p. 424.
12. 'Introduction to Science' (Temple Encyclop. Primers), p. 32.
13. Ibid. p. 38.
14. 'Animal Life,' pp. 224–5.
15. 'The Formation of Vegetable Mould,' &c. p. 315.—In the words of G.H. Lewes, "Light, colour, sound, pain, taste, smell are all states of consciousness, and nothing more. Light with its myriad forms and colours—sound with its thousandfold like—make nature what nature appears to us; but they are only the investitures of the mind. Nature is an eternal Darkness—an eternal Silence."
16. "Beyond the reach of the microscope, there are still worlds of events in nature which we can never see, although we may infer the existence of some of them in other ways."—G.J. Storey (Sci. Proc. R. Dubl. Soc. n.s, vol. viii. p. 230).
17. Cases of atrophy following disease appear to be always attended by a corresponding increase of other organs; blind animals always possess very strongly developed organs of touch, hearing, and smell." Cf. Weismann, 'Lectures on Heredity,' &c., 2nd ed. vol. i. p. 88.
18. "What we, therefore, distinguish as light and colour arises from a subjective property of the retina, inasmuch as it only reacts on certain other vibrations. We might therefore imagine the existence of eyes which could not perceive the intermediate parts of the spectrum as ours can, but only the rays situated at the invisible ends. To such eyes the world would have quite a different aspect." Cf. Bernstein, 'The Five Senses of Man,' p. 104.
19. 'Ants, Bees, and Wasps,' p. 220.
20. Pres. Addr. Biol. Soc. Washington. Cf. 'Nature,' vol. lii. p. 210.— An article appeared on "Animal Vision" in the 'Spectator,' June 8th, 1895, which was really a contribution to the study. The writer remarked:—"There is little positive evidence that the larger quadrupeds, Oxen, Deer, the Felidæ, or Dogs, have much sense of colour."
21. Prof. Plateau affirms that "the admiration of insects for flowers does not exist." (Mém. Soc. Zool. de France, vol. xiii. 1900. Cf. summary of same papers, Ent. Month. Mag. 1901, p. 211.)
22. 'The Wonderful Trout,' p. 42.
23. 'Bull. de l'Acad. Roy. de Belgique,' 1887, 1888.
24. 'Trans. Ent. Soc.' 1889, pp. 407–8.
    Dr. Sharp has elsewhere described the compound or faceted eyes of insects as being "totally different in structure and very distinct in function from the eyes of Vertebrata, and are seated on very large special lobes of the brain, which indeed are so large and so complex in structure that insects may be described as possessing special ocular brains brought into relation with the lights, shades, and movements of the external world by a remarkably complex optical apparatus" ('Cambr. Nat. Hist.' vol. v. p. 98).
25. 'Sci. Proc. R. Dubl. Soc' n.s. vol. viii. p. 238.— Cf. Joh. Müller ('Zur Vergleichenden Physiologie des Gesichtssinnes,' p. 322), and Burmeister ('Manual Entomology,' Eng. transl. p. 489).
26. 'Nature,' vol. xi. p. 6.
27. J.J. Murphy, ibid. p. 28.
28. Imperfect vision is a frequent cause of illusion. Prof. Sidgwick's Committee of the "Society for Psychical Research" were acquainted with a short-sighted friend who had several times mistaken a "projecting corner of a rough stone wall for a lady with flounced skirts" ('Edinburgh Review,' January, 1895, p. 98).
29. Mr. Hickson has pointed out that in some fishes of the deep sea (Scopelidæ), "not being provided with well-developed eyes or phosphorescent organs to attract their prey, the pectoral fins and the outer rays of the pelvic fins have become elongated, and provided with special sense organs for searching for their food in the fine mud of the floor of the ocean" ('The Fauna of the Deep Sea,' p. 159).—There is a general similarity in the colouring of animals inhabiting these depths with the mud of the ocean floor, but "protective resemblance" can scarcely be claimed when the tactile sense compensates for the loss of sight.
30. 'Origin of Species,' 6th ed. p. 145.
31. 'Darwinism,' p. 130.
32. Barrow, 'Trav. Interior of Southern Africa,' vol. i. p. 110.
33. 'Among Cannibals,' pp. 142–3.
34. Cf. 'Descent of Man,' 2nd ed. pp. 33–4.
35. 'History of Creation,' 4th ed. vol. i. p. 269.
36. By many evolutionists who advocate Darwinism as sanctioned by Weismannism, it has recently become the vogue to not only decry Lamarck, but to denounce what they consider as the Lamarckian heresy. Not only have his views been condemned and ridiculed, but even his honesty has been called in question. Thus a recent writer, after remarking on the extraordinary coincidence of the independent conception of "Natural Selection" by Darwin and Wallace, cannot adopt the same view as to some coincidences in the writings of Lamarck and Erasmus Darwin; and although the first named, in his 'Animaux sans Vertébres,' states that his theory is the first that has been presented, this does not satisfy the suspicions of his critic, who writes:—"But if Lamarck borrowed without acknowledgment, it would be but a small step further to write the passage in question" ('Nature,' vol. lii. p. 362). Prof. Osborn, in his 'From the Greeks to Darwin,' has examined, discussed, and reduced this imputation to the character of "unproved slander." How different is the verdict of one well able to judge. Huxley writes of "the famous naturalist Lamarck, who possessed a greater acquaintance with the lower forms of life than any man of his day, Cuvier not excepted, and was a good botanist to boot" ('Collected Essays,' vol. ii. p. 11). And again he remarks:—"The Lamarckian hypothesis has long since been justly condemned, and it is the established practice for every tyro to raise his heel against the carcase of the dead lion" (ibid. p. 12). When the devoted disciples of Weismann, aghast at the least argument for some amount of direct environmental change or inheritance of acquired character, raise the cry of "Lamarckism," we are reminded of the XXXII controversial stratagem described by Schopenhauer:—"If you are confronted with an assertion, there is a short way of getting rid of it, or, at any rate, of throwing suspicion on it, by putting it into some odious category; even though the connection is only apparent, or else of a loose character. You can say, for instance, 'That is Manichæism,' or 'It is Arianism,' or 'Pelagianism,' or 'Idealism,' or 'Spinozism,' or 'Pantheism,' or 'Brownianism,' or 'Naturalism,' or 'Atheism,' or 'Rationalism,' 'Spiritualism,' 'Mysticism,' and so on" ('The Art of Controversy,' Bailey Saunder's transl. pp. 41–2).
37. H.M. Bernard has apparently used a similar argument for "the transmission of acquired characters by inheritance, this inheritance coming in as a natural term at the end of a long series of individual acquirements" ('Nature,' vol. I. p. 546).
38. According to Topinard, "the organ of vision is similar in man, the anthropoid apes, the pithecians, and the cebians" ('Anthropology,' p. 95).
39. This may also be illustrated by the perceptions of persons suffering from red-blindness. As Bernstein observes:—"The world must appear to them quite differently coloured to what it appears to us. What looks to us white, must to them have a greenish-blue appearance, because red is wanting in it; and yet they call it white, because it comprehends the whole of their series of colours" ('The Five Senses of Man,' p. 115). Even our own sense perceptions may be only temporary. We call a body white when it reflects all the colours of the spectrum in the proportions in which they are contained in sunlight. As Bernstein further remarks:—"It is very probable that the kind of light which we call 'white' would not remain the same if the proportion of the colours in the light of the sun were to alter; and since we suppose even the sun and its light may not remain the same for ever, it is quite possible that our descendants may have a perfectly different idea of white to what we now have" (ibid. p. 162).
40. "Animal Behaviour," Biol. Lect. Marine Biol. Lab, Wood's Holl, Mass. 1898, p. 293.
41. 'Miss. Trav. and Research in S. Africa,' p. 136.
42. 'A Naturalist in Mid-Africa,' p. 247.
43. 'Obs. Geol. and Zool. Abyssinia,' p. 248.
44. 'Introd. Study Fishes,' p. 111.
45. Cf. Seeley, 'Freshwater Fishes of Europe,' p. 271.
46. Probably is meant: Serolis neaera Beddard 1884. (Wikisource-ed.)
47. 'Natural Science,' vol. vii. p. 56.
48. Cf. 'The Five Senses of Man,' p. 163.
49. Ibid. pp. 162–3.