Page:Popular Science Monthly Volume 36.djvu/407

Rh from some species of Asellus hardly admits of a doubt. Our Asellus communis abounds under sticks and stones, submerged boards and logs, throughout the Northern and central States. Thence it could readily be carried, in cavernous regions like those of southern Illinois, Indiana, and Kentucky, into subterranean streams. The supply must be very great, as the individuals of C. stygia are very abundant; indeed, so far as we know, as much as or even more so than those of Asellus communis.

In the blind crayfish of the caverns of Indiana and Kentucky, and of the similar species (C. hamulatus) inhabiting the Nickajack Cave of Tennessee, we have two aberrant forms belonging to a widely diffused group, whose center of distribution lies in the Mississippi Valley, and which is rich in species and in individuals. All the streams and ditches situated over or near the caves are densely populated with crayfish. I was interested, after finding C. pellucidus in a stream flowing through the Bradford Cave, near New Albany, Indiana, to find the common eyed crayfish of that region in great abundance a few yards from the mouth, outside of the cave, in the shallow brook issuing from the cave itself. That crayfish with eyes can readily enter a cave—probably in time of freshets—is proved by the fact that Cambarus Bartonii is often found in Mammoth Cave, where it finds food; and a small specimen has been found by Mr. Putnam a little paler than usual—i. e., as pale as the darker specimens of C. pellucidus—but the eyes were normal, though it is doubtful if it lives long enough in the cave to breed there.

The nearest out-of-door ally of Cambarus pellucidus is Cambarus affinis. On the other hand, the nearest lucicolous ally of C. hamulatus is perhaps C. latimanus.

It is instructive to find that, in regard to the development of the eyes, and the slenderness, size, and color of the body, these two cave crayfish closely resemble each other, though obviously originating, as Prof. Faxon states, from species belonging to quite different sections of the genus Cambarus, and to a different, more southern, river valley. These facts appear to prove beyond question that the cave species of crayfish in the United States have descended from quite different species of Cambarus, belonging to different zoögeographical areas. Had the two species of blind crayfish been produced instantaneously by special creation, as popularly supposed and advocated in the past by some naturalists, why should the accessory genital organs (gonopoda) differ so much that on this account they belong to different sections of the genus Cambarus?

The cave Phalangidæ, or harvest-men, whose habits and distribution in Europe as well as the United States, both as regards lucicolous and cavernicolous forms, have been given in much