The Dawn of Reason | Page 4

discussed.
CHAPTER I
THE SENSES IN THE LOWER ANIMALS
I am inclined to believe that the primal, fundamental sense,--the sense of touch,--from which all the other senses have been evolved or developed, has been in existence almost as long as life.
It is quite probable that it is to be found in the very lowest animal organisms; and, if our own senses were acute enough, it is more than probable that we would be able to demonstrate its presence, beyond peradventure, in such organisms.
The senses of taste and smell, according to Graber, Lubbock, Farre, and many other investigators, seem to be almost as old as the sense of touch. My own observations teach me that certain actinophryans,[5] minute, microscopic animalcules, can differentiate between the starch spores of alg? and grains of sand, thus showing that they possess taste, or an analogous sense.
[5] Vide the writer, N. Y. Medical Record, August 15, 1896.
On one occasion I was examining an actinophrys (Actinophrys Eichornii), which was engaged in feeding. It would seize a rotifer (there were numerous Brachioni in the water) with one of its pseudopodia, which it would then retract, until the captured Brachionus was safely within its abdominal cavity. On the slide there were several grains of sand, but these the actinophrys passed by without notice.
I thought, at first, that this creature's attention was directed to its prey by the movements of the latter, but further investigation showed me that this was not the case.
After carefully rinsing the slide, I placed some alga spores (some of which were ruptured, thus allowing the starch grains to escape) and some minute crystals of uric acid upon it. Whenever the actinophrys touched a starch grain with a pseudopod, the latter was at once retracted, carrying the starch grain with it into the abdominal cavity of the actinophryan; the uric acid crystals were always ignored.
I conclude from this experiment, that the actinophrys, which is exceedingly low in the scale of animal life, recognizes food by taste, or by some sense analogous to taste.
Many species of these little animals, however, are not as intelligent as the Eichorn actinophrys; they very frequently take in inert and useless substances, which, after a time, they get rid of by a process the reverse of that which they use in "swallowing." By the latter process they put themselves on the outside of an object--in fact, they surround it; by the former, they put the object outside by allowing it to escape through their bodies.
The sense of sight makes its appearance in animals quite low in the scale, therefore the reader will pardon me if, while discussing this sense, I prove to be a bit discursive. The subject is, withal, so very interesting that it calls for a close and minute investigation.
One of the immutable laws of nature declares that animals which are placed in new surroundings, not fatal to life, undergo certain changes and modifications in their anatomical and physiological structures to meet the exigencies demanded by such a modification of surroundings. Thus, the flounder and his congeners, the turbot, the plaice, the sole, etc., were, centuries and centuries ago, two-sided fishes, swimming upright, after the manner of the perch, the bass, and the salmon, with eyes arranged one on each side of the head. From upright fishes, swimming, probably, close to the surface of the sea, they became dwellers on its bottom, and, in order to hide themselves more effectually from their enemies or their prey, they acquired the habit of swimming with one side next to the ground, and of partially or wholly burying themselves in the mud, always, however, with one side down. They thus became flat fishes, losing the coloring of their under surfaces, and their eyes migrating across their foreheads and taking up positions on the upper surfaces of their heads. Again, when animals are placed among surroundings in which there is no need for some special organ, this organ degenerates, and passes wholly or partially into a rudimentary condition, or, entirely out of existence. These latter effects of changed conditions on animals are especially noticeable in the effect of continual darkness on the organs of sight of those creatures which, owing to said mutations, have been compelled to dwell in darkness for untold ages.
The mole, far back in the past, had eyes, and gained its livelihood above ground in the broad light of day; but, owing to some change in its surroundings, it was forced to burrow beneath the surface of the earth; consequently its organs of sight have degenerated, and are now practically worthless as far as vision is concerned. All moles, however, can tell darkness from light, consequently, are not wholly blind--a certain amount of sight remains. This is due to the fact that, although the optic nerve, on examination, is invariably found to be atrophied