THE EFFECTS OF CAVE LIFE ON ANIMALS. 39 i 



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, Lep- 

 todera, 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 environ- 

 ment 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 color- 

 less or whitish, more or less vitreous, and pellucid, the pigment 

 cells being degenerate and functionless. The effects of total dark- 

 ness 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 

 Chernetidaz 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 dark- 

 ness are the following : 



1. Total atrophy of optic lobes and optic nerves, with or with- 

 out the persistence in part of the pigment or retina and the crys- 

 talline lens (Cozcidotaia, Crangonyx, Chthonius, Adelops, Pseudo- 

 tremia). 



2. Persistence of the optic lobes and optic nerves, but total 

 atrophy of the rods and cones, retina (pigment) and facets (Or- 

 conectes). 



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 



