98 FAUNA OF MAYFIELD'S CAVE. 



sists of a great number of species of spiders living for the most part in 

 shady woods, among the lower branches of plants, under leaves, and in 

 caves and cellars. " (Emerton, 1902, 134.) 



Throughout this paper constant mention has been made of the rela- 

 tives of cave species and in nearly every case cave species have been 

 shown to have relatives either in caves or in similar dark, moist places. 



Species of animals found in caves belong to families and genera 

 which live in more or less dark and shady places outside of caves. 

 These families and genera are predetermined, so to speak, toward cave 

 life, and it is from these groups and other such groups that cave faunas 

 are derived. 



Further, in many cases, other species of the same groups to which 

 cave species belong are adapted for cave life but have not found a cave 

 to occupy, and hence are not cave species. The Amblyopsidae (cf . Cox, 

 1905, 379) agree in having a relatively high degree of development of 

 the tactile ridges and a low grade of development of the eye. Of the 

 8 species known all but 2 are inhabitants of caves and those two are ap- 

 parently capable of cave existence. One of them lives in the rice 

 ditches in South Carolina and in the Dismal Swamp and in other similar 

 places on the Atlantic Coast. The other has been found only in Illinois 

 in a spring which is the outlet of an underground stream. It approaches 

 the Chologaster agassizii of Mammoth Cave in its adaptations for 

 underground existence, having been shown capable of securing its food 

 without the use of its eyes (Eigenmann, 1900-6, 402). The California 

 goby (Eigenmann, 1890) , of another family of fishes, lives in holes in 

 the beach between tide-marks. It is lighter in color and has more 

 degenerate eyes than the C. agassizii of Mammoth Cave. H. Garman 

 (1892, 241) found a species of Anopthalmus {A. horni) in and about 

 crevices of the rocks in an open quarry at Lexington, Kentucky. Sayce 

 (1901) has described 3 species of blind crustaceans— an amphipod and 

 2 isopods— from a surface stream in Australia. There are every year 

 being described new species of blind and pigmentless crustaceans from 

 wells, springs, and underground streams in various parts of the world. 

 They are known from the United States, England, several countries of 

 continental Europe, New Zealand, Tasmania, Australia, and Algeria, in 

 some of which countries there are no caves whatever. Specialists 

 doubtless are familiar with animals of many groups equally as well 

 suited to cave life but which live in caveless regions. 



Animals become cave inhabitants because they are structurally and 

 physiologically suited to life in caves. They are predetermined cave 

 inhabitants and enter caves because there they find conditions suit- 

 able for their existence. 



