Page:Popular Science Monthly Volume 36.djvu/405

Rh green nor brown, like the two species of the upper world, but pellucid, bleached out, or colorless.

Such was also found by Dr. Joseph to be the case with the smaller crustaceans, such as certain cave species of Cypris, Leptodera, Estheria, and Branchipus (B. pellucidus Jos.).

3. As regards change of color, we do not recall an exception to the general law that all cave animals are either colorless or nearly white, or, as in the case of Arachnida and insects, much paler than their out-of-door relatives.

The worms (planarians and earth-worms) are somewhat paler than their allies living out of caves, but as the normal environment of most planarians and earth-worms is much like those of cave animals, the difference is not so marked, though both of our cave planarian worms are white and eyeless.

All the cave Crustacea, both aquatic and terrestrial, are colorless or whitish, more or less vitreous, and pellucid, the pigment cells being degenerate and functionless. The effects of total darkness seem quite different from the influence to which the eyeless deep-sea Crustacea are exposed, since they, like their fellows with eyes normal or hypertrophied, are said to be of the same flesh and reddish tints common to deep-sea animals.

In the case of the cavernicolous myriapods the bleaching of the body is very marked. In out-of-door myriapods the normal tint of the integument is brown or rarely amber-brown; but the color of the cavernicolous species is white or flesh-white, like a freshly molted myriapod of normal habitat.

The cave species of Arachnida are usually whitish or pale amber-colored, or pale horn, with a reddish tint. Of the mites, some are white, others horn-color, or chitinous. In the family Chernetidæ the cave species are "dull white," or "pale horn with a reddish tint," or "pale yellowish."

The effects upon the eyes and optic lobes of a life in total darkness are the following:

1. Total atrophy of optic lobes and optic nerves, with or without the persistence in part of the pigment or retina and the crystalline lens (Cæcidotæa, Crangonyx, Chthonius, Adelops, Pseudotremia).

2. Persistence of the optic lobes and optic nerves, but total atrophy of the rods and cones, retina (pigment) and facets (Orconectes).

3. Total atrophy of the optic lobes, optic nerves, and all the optic elements, including rods and cones, retina (pigment) and facets (Anophthalmus, Scoterpes, and? Anthrobia).

An interesting fact confirmatory of the theory of occasional rapid evolution, as opposed to invariably slow action involved in pure Darwinism, is that we never find any rudiments of the optic