THE EFFECTS OF CAVE LIFE ON ANIMALS. 393 



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 subterra- 

 nean 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 Nicka- 

 jack 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 speci- 

 men 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 Cam- 

 barus 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 origi- 

 nating, as Prof. Faxon states, from species belonging to quite dif- 

 ferent sections of the genus Cambarus, and to a different, more 

 southern, river valley. These facts appear to prove beyond ques- 

 tion that the cave species of crayfish in the United States have de- 

 scended from quite different species of Cambarus, belonging to 

 different zoogeographical areas. Had the two species of blind 

 crayfish been produced instantaneously by special creation, as 

 popularly supposed and advocated in the past by some natural- 

 ists, 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 Phalangidce, or harvest-men, whose habits and dis- 

 tribution in Europe as well as the United States, both as regards 

 lucicolous and cavernicolous forms, have been given in much de- 



VOL. XXXVI. 25 



