416 ON THE WYANDOTTE CAVE AND ITS FAUNA. 
Orconectes bears the same relation to Cambarus; Stygobromus 
bears nearly the same to Gammarus, and Scoterpes is Spiros- 
trephon without eyes, and no pores. 
Secondly, as to variability. I have already shown that in 
Gronias nigrilabris, the blind Silurid from the Conestoga in Penn- 
sylvania, that while all of several specimens observed were blind, 
the degree of atrophy of the visual organs varies materially, not 
only in different fishes, but on different sides of the same fish. In 
some the corium is imperforate, in others perforate on one side, in 
others on both sides, a rudimental cornea being thus present. In 
some, the ball of the eye is oval and in others collapsed.: This 
fish is related specifically to the Amiurus nebulosus of the same 
waters, more nearly than the latter is to certain other Amiuri of 
the Susquehanna river basin to which the Conestoga belongs, as 
for instance the A. lyn; it may be supposed to have been enclosed 
in a subterranean lake for a shorter time than the blind fishes of 
the Western Caves, not only on account of the less degree of loss 
of visual organs, but also in view of its very dark colors. A . 
feature on which I partly relied in distinguishing the species, has ; 
perhaps a different meaning. The tentacles or beards were dèe 
scribed as considerably shorter than those of allied species. On : 
subsequently examining a number of individuals, I was struck with = 
the irregularity in their lengths, and further inspection showed a 
that the extremities were in each case enlarged, as though yt 
cicatrix. I have imagined that the abbreviation of the tentacles : 
is then due to the attacks of carnivorous fishes which inhabit the a 
subaérial waters into which the Gronias strays, from whom its 
blindness renders it unable to protect itself. 
Thirdly, it is asserted that the young Orconectes possess eye 
and that perhaps those of the ~Typhlichthys do also. if ap a 
statements be accurate, we have here an example of whatis ent a. 
to occur elsewhere, for instance, in “the whalebone whales- ih . 
foetal stage these animals possess rudimental teeth like other > oo 
cea, which are subsequently absorbed. This disappuwwnt pe 
eyes is regarded with reason by Prof. Wyman as evidence & ee 
descent of the blind forms from those with visual organs: x ae - 
suggest that the process of reduction illustrates the law of a 
dation,” accompanied by another phenomenon. Where @N 
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teeth, and the presence of an additional pair of pyloric ceca, which he men 
be apt to prove only epee’ fic. 
