ORIGIN OF CAVE LIFE. 103 



Two other blind fish {Typhlichthys osborni from Horse Cave, Ken- 

 tucky, and Typlilichthys ivyandotte from Wyandotte Cave, Indiana) 

 very closely resemble T. subterraneus and the others. The different 

 species of cave crayfishes (Cambarus) resemble each other very closely, 

 so that, according to W. P. Hay (1902, 436), while C hamulatus and C. 

 pellucidus differ considerably in their affinities, their appearances are so 

 strikingly similar "that without a careful examination it would be ex- 

 ceedingly difficult to distinguish the two species." Another instance 

 of convergence is seen in the so-called "cave crickets." Speaking of 

 these cave-inhabiting Ceuthophili, Sharp (1899, 321) says: 



The species with this habit, though found in the most widely separated parts of 

 the world, have a great general resemblance, so that one would almost suppose the 

 specimens found in the caves of Austria, in the Mammoth Cave of Kentucky, and in 

 the rock-cavities of New Zealand to be one species, although they are now referred 

 by entomologists to different genera. 



There is not, however, a general uniformity in the peculiar modifi- 

 cations of cave animals. Some cave species have one structure highly 

 modified, others another, still others appear to have no highly modified 

 organs to compensate for the loss of visual organs. Chilton (1894, 269), 

 reviewing this point with reference to the New Zealand subterranean 

 Crustacea, shows that while some have additional sensory setae, others 

 have not, that while some are slender-bodied, others are not, and while 

 the appendages in certain cases are lengthened, in others they are not, 

 ' 'while there is no sign of a similar modification in Crangonyx compac- 

 tus, which has the body normally stout, the antennee and legs of only 

 moderate length, and the uropoda even somewhat short and stumpy" 

 (1894, 269). This same Crangonyx compactus is white, has very de- 

 generate eyes, and is an exclusively subterranean form. Further, 

 Chilton compares various forms and shows that when elongation of an 

 appendage takes place, it is in one joint in one species and in another in 

 another species. 



The question arises whether the modified cave forms are entitled to 

 rank as distinct species and genera. They are not distinct species in 

 the de Vriesian sense. According to de Vries (1905) a new species 

 must have a new character. Certain cave spiders lack pigment and their 

 eyes are poorly developed, but they have acquired no new character. 

 So with other cave animals. The genus Anopthalmus has been discarded 

 by European authorities because species have been found showing every 

 gradation between a species without trace [of eye or optic lobes, a typical 

 Anopthalmiis, and species of Trechtcs with eyes. Cope's genus Orconectes 

 (Cope, 1872, 173), proposed for the species of blind crayfish, has failed 

 to meet with acceptance. Cxcidotea differs from Asellus in about the 



