Democratic Sentinel, Volume 11, Number 45, Rensselaer, Jasper County, 2 December 1887 — The Living Inhabitants of Caverns. [ARTICLE]

The Living Inhabitants of Caverns.

The living inhabitanta of caverns, those which make these regions of continuous darkness their abiding places, are numerous and of the greatest interest to the naturalist Of the several hundred species known to students, by far the greatest part belong to the group of articulated animals, insects, and crustaceans, these being the forms which, of all animals, are the most varied in structure and best suited for the odd chances of life which the caverns afford. As the reader well knows, the great problem now before science is to determine how far the shapes of living creatures are determined by the circumstances of the world about them, and how'-’far this determination has been brought about through a process of selection, in a natural way, of those varieties which have some accidental special fitness for the condition in which they live. Cavern animals afford us a capital bit of evidence toward the solution of this problem. The prevailing close affinity of their forms with those which live in the upper world of sunshine and changing seasons shows, beyond question, that they are all deprived from similar forms which once dwelt in the ordinary conditions of animal life. What, then, are the effects arising from this complete change in the circumstances of these underground creatures? The facts are perplexing in their variety, and by no means well worked out, but the following points seem to be well established, viz.: There is a manifest tendency of all gayly colored forms to lose their hues in the caverns, and to become of an even color. This may be explained by the simple absence of sunshine, and on it no conclusions can be based. The changes of the structural parts are of more importance; these, as might be expected, relate mainly to the organs of sense. The eyes show an evident tendency in all the groups to fade away. In the characteristic cavern-fishes they have entirely disappeared, the whole structure which serves for vision being no longer produced. In the cray-fishes we may observe a certain gradation. Some species which abound in caverns are provided with eyes; others have them present, but so imperfect that they cannot serve as visual organs; yet others want them altogether. One species of pseudo-scorpion, as shown by Professor Hagan, has in the outer world four eyes, while in the caves it has been found with two eyes, and others in an entirely eyeless condition. Some cavern-beetles have the males with eyes, while the females are quite without them. As a whole, the cavernforms exhibit a singular tendency of the visual organs, not only to lose their functions, but also to disappear as body-parts. At the same time there is an equal, or even more general, development of the antennae and other organs of touch; these parts become considerably lengthened, and apparently of greater sensitiveness, a change which is of manifest advantage to the individual.—Scribner's Magazine.