iroSEDM OF COMPAKATIVE ZOOLOGY. 235 



healthy, and as lively as when first taken from the well. If not capable of 

 long fasts, he must Uve on small organisms my eye cannot discern. He is 

 hardly ever still, but moves around the sides of the vessel constantly, down 

 and up, as if needing the air. He never swims through the body of the water 

 away from the sides, unless disturbed. Passing the finger over the sides of the 

 vessel under water, I find it slippery. I am careful not to disturb this slimy 

 coating when the water is changed. . . . Numerous tests convince me that it 

 is through the sense of touch, and not through hearing, that the fish is dis- 

 turbed : I may scream, or strike metal bodies together over him as near as 

 possible, yet he seems to take no notice whatever. If I strike the vessel so 

 that the water is set in motion, he darts away from that side through the mass 

 of the water, instead of around, in his usual way. If I stir the water, or touch 

 the fish, no matter how lightly, his actions are the same." 



From the stomach of one specimen the remains of an Asellus were 

 taken; from that of another, a young Camharus ; from a third, frag- 

 ments of an insect resembling Ceuthophilus ; and from others, portions 

 of a crustacean, of which we have several specimens from Day's Cave, 

 with well developed eyes, resembling Crangonyx, and from appearance 

 the main food dependence. 



The total length of the largest fish is two inches and a quarter. The 

 eggs in the ovaries, August to September, are large, but with uo traces 

 of embryos. 



CRUSTACEA. 



In part, at least, the problem of the origin of the cave Crustacea is 

 simplified by the fact that they are so distinct in various caves as to 

 leave no doubt that they are descended from ancestors already of dif- 

 ferent species at the time of entering the subterranean habitations. The 

 blind crayfish of the Missouri caves is very distinct from any previously 

 known ; it is described below under the name Cambarus setosus. The 

 common species of the neighborhood, C. virilis, is also found to enter 

 the underground retreats, but it is not, of the outside forms, the nearest 

 ally of the blind form. The latter bears so much affinity to C. Bartonii 

 as to suggest derivation from it. A somewhat parallel condition exists in 

 the caves of Missouri and those of Kentucky. In these last, with the blind 

 C. pellucidus we find C. Bartonii, the nearest ally of the blind crayfish 

 of Missouri, C. setosus ; and with the latter again, in the Missouri caves, 

 is found an eyed species, C. virilis, more nearly allied to the blind one 

 in the Mammoth Cave. The relationship existing between the species 

 C. setosus and C. Bartonii is much closer than that between C. pellucidus 

 and C virilis. A distribution of C. Bartonii covering so large a portion of 



