Rensselaer Semi-Weekly Republican, Volume 37, Number 1, Rensselaer, Jasper County, 3 January 1905 — IN THE LOWER ORDER. [ARTICLE]

IN THE LOWER ORDER.

Two Extremes of Animal Eyesight. If we could see an eye which has actually been evolved from one like that of amphloxus, let us examine the head of a lizard. Disregard for a time his bright eyes, one on each side of his head, and look directly down on the center of the skull between them. Here we will find an oddly shaped scale marked with a little depression and this is, indeed, what is left of our Cyclopean eye in the tiny sand creature. Lizards doubtless derive very little benefit from it, as the nerve leading from it is very small, but in some of their ancestors it must have been of great value in detecting the presence of enemies from above. In all creatures above lizards this third median eye (called the pineal) is found although of no use whatever; this persistence, perhaps, showing of what great importance it once was. In a chick in the early stages of incubation this eye is very considerably developed, while yet the paired eyes are but small structures. But suddenly Nature seems to realize that the old regime has passed—tnat the little bird will need other more modern eyes, and the two sides begin to develop with wonderful rapidity, and soon catch up with and distance the Cyclops eye, whose early start ends only in promise. There was certainly a time long ago when living creatures were not blessed with eyes. In creatures now living upon the earth, we may trace a series of eyes from the highest and most efficient to the simplest dot of black pigment. The eye of the eagle may stand for the first, and the eye-spot of the amphioxus or the eight sense-germs of a. jellyfish for the other extreme of the series. The amphioxus is a little worm, or fishlike creature which most of the time lives buried in the sand of our seashores. He is interesting and important out of all proportion to his size, two inches, for he is ome of the lowliest creatures to be honpred with a backbone, the class-mark of all higher animals. He has no skull and no brain, but near the front end of the thin thread of nerve (the foreshadowing of our spinal chord) is a tiny black dot. By means of this he distinguishes light from darkness, which is all his simple life requires. Let us not forget the position of this single, most primitive of .eyes—in the center of what would be the brain if the lowly creature had one.

The eye of the jellyfish is so primitive that we can hardly »ay whether it sees er leeiS. That is, when a floating jellyfish begins to sink below thesurface of the water as the shaaow of an advancing ship falls upon it, it is probably affected by the sensation of darkness, but perhaps the pressure of the onrush wave has something to do with it. A horse, a bat, a mole, a monkey, a seal , all have a trace of this third eye, and when we put a finger on the “soft spot” of the head of a tiny baby, we realize the wonderful import of it — that the softness is due to a near approach of this same third eye to the surface, striving as it has done in so many lower creatures to push its poor Imperfect lens to where the light can act. upon it. But the old ways have given place to new, and the child’s blue eyes look out at you and the Wo; Id and see all that is necessary for its life and needs. r We can hardly iniagi",' afiy.LLC more the loss of our JJcsignt, and yet there are many creatures which have found life moie pleasant in the darkness of caves and underground tunnels or to roam only at night, when there eyes are useless, and by the lack of use these organs have degenerated to mere specks and in some cases the skin has grown completely over them. Thus we find blind fishes and lizards in. dark caves, and blind ants and moles all but blind in their dark subterranean homes. Certain bats, too, have but tiny dots for eyes, and depend chiefly upon their acute hearing and some sense by which they can feel the 'vibrations of the air. Snakes have but poor eyesight, and like fish have no Eyelids. Their eyes are covered with a thin, transparent scale which is ever open, la sun and shade, at noon and midnight, in an awful, never-winking stare. We cannot imagine how sleep can ever come to such creatures. Finally, let us turn to the most perfect eye nature has ever produced. We can read and write and do many things by the aid of our eyes that are forbidden to other creatures of the earth; but this is because of the brain behind directing the eyes. We can look closely at the stars, and we can watch the actions or a tiny dot of life many thousand of times smaller than a mote of dust. All this we can do by means of the two “magic tubes," the telescope and the microscope. But when the unaided eye is alone considered, birds put us to shame. “Observe an eagle,” writes a noted scientist, “soaring aloft until he seems to be but a speck in the blue expanse. He is far-sighted, and scanning the earth below, descries an object much smaller than himself, which would be invisible to us at that distance. He prepares to pounce upon his quarry; in the moment required for the deadly plunge he becomes near-sighted, seizes his victim with unerring aim, and sees well how to complete the bloody work begun. A humming bird darts so quickly that our eyes cannot follow him. yet instantaneously settles as light as a feather upon, a tiny twig. How far off it was when first perceived we do not know, "but in (he intervening fraction of a second the twig has rushed into the focus of distinct vision from many yards away. A woodcock tears through the thickest cover as if it was clear space, avoiding every obstacle. The only things to the accurate perception of which birds’