CnrSTACEAXS OF XTCKAJACK CAVE— HAY. 



428 



Orconedes to contiiin th»^ h\\\\({ criiytishes. These in their \w^\ possess 

 the very characters which h:i\c hecii yi\('ii i»-eiieri(' \ahie in Ca^cidoted,- 

 they are white, eyeless, and more elong-ate than the sui'face dwellers, 

 hut there can be no doubt that the live or six known species ol" blind 

 craylish have had an altogether independent origin and ai'e less closelv 

 related to each othei- than to species with eyes living outside the oaves. 

 The remarks of llag(Mi' regarding the in\alidity of the genus (}r<-<>~ 

 neetes may ^ery ^vell apply here. 



On looking at the general characters of cave-inhabiting animals it 

 will l)e seen that nearly all have been affected in the same general way; 

 loss of color, more or less complete degeneration of the eyes, and a 

 corresponding hypertrophy of the tactile organs are characteristic. 



In some gi-oups (for instance, the Amph/jxHhi) thei-e haNc tteeri 

 found intermediate forms l)et-\veen the surface and true sul)tei-ninean 

 \ arieties. l)ut so far this has not been accomplished with the Isopods. 

 Packard mentions a case, however, which is extremely sviggestive; a 

 specimen of ^1. coi/iiinnus from a well in southern Indiana was Ideached 

 perfectly white, but retained all the other char- 

 acters of its species. It is a well-known fact that 

 occasionally (\ xfygi'i has on the top of its head, 

 where its eyes shoiTld })e, a few facets, showing 

 that the loss of eyes has been so recent that indi- 

 \ iduals occasionally revert to the primitive char- 

 acters. However, there is lacking at the present 

 time the positive evidence that this genus is not 

 a natural one, or that we iind here a case of the 

 independent development of similar characters. 

 I therefore accept the genus on tiie grounds of 

 convenience, feeling certain that futur(^ investi- 

 gations will throw light on its origin. 



MANCASELLUS MACROURUS Harger. 



This species was o))tained in some abundance 

 at various localities in the region visited. 1 

 found it first in the John Ross spring at Ross- 

 ville, Georgia, where it inhabited the cold water 

 close to the rock crevices from which the spring- 

 issued. Beyond 20 or 30 feet downstream it ceased to occur. At 

 Xickajack Cave it was fairlv a])undant just outside the cave, on tlie 

 underside of flat rocks and in the crevices of decaying logs of wood. 

 It was most common in a dimly lighted crevice at the mouth of a 

 tunnel- like outlet, for the pool at the front of the ca\e, where in 

 a few minutes I picked some fifty specimens from some submerged 



' Hagen, Amer. Nat., VI, 1872, p. t<)4. X()tc> ali-n the genus Slyijohi 

 for tlie siibterranean (huiniKiridn-, Ahum-. Nat.. W, July, 1872, p. 422. 



Coi)e, 



