PODOPTHALMATA ASTACID^E. 71 



to swim caudal end foremost without first turning about and really 

 swims toward its pursuer. But the moment it begins to swim it either 

 turns squarely over ventral side up or turns to one side so as to move 

 in the direction in which it was crawling. After changing the direction 

 of its course it rights itself and soon disappears if there is ready means 

 of concealment. In its swimming and crawling motions this crayfish 

 is not less active than other crayfish. 



This species is sensitive to a jar in the water at a distance of several 

 feet if the disturbance is quite pronounced, like that produced by drop- 

 ping a pebble into the pool. But considerable rippling or slow swishing 

 about in the water often fails to produce any effect upon individuals at 

 a little distance. It seems insensible to sound, although a heavy jar on 

 the bank of the pool may cause it to move. Light often fails to have 

 any apparent effect, but on two occasions when a bright light was sud- 

 denly flashed upon perfectly quiet individuals they moved immediately, 

 swimming rapidly from the lighted area. In these two cases there 

 could have been no jar or other disturbance, for I had quietly crept to 

 near the individuals from a distance and then suddenly thrown the light 

 full upon them. Sometimes when the light was held upon individuals 

 for several minutes they failed to respond at all; usually, however, they 

 moved after two or three minutes. 



From observations upon C. pellucidus testii which Dr. Charles Zeleny 

 kept in the laboratory, I believe they molt fronf two to four or five times 

 a year, depending upon the size, the smaller or younger ones molting 

 oftener. Putnam (18756, 18) kept a specimen of C. pellucidus from 

 Mammoth Cave for six months and it molted twice during that time. 

 Just after molting C. pellucidus is very transparent, so that it is a 

 veritable chart of crayfish anatomy, the nerve-cord and ganglia and 

 alimentary canal showing through the body wall in detail. In one which 

 had molted two or three days previously the "stomach mill" was seen in 

 full operation while it was eating a bit of beef. This crayfish is ordi- 

 narily white, its body wall becoming more or less opaque soon after 

 molting. Large individuals which evidently have not molted for some 

 time become quite dark or dirty rusty in appearance from the collection 

 of dirt upon the shell. 



As to the food of C. pellucidus testii within the cave, very little has 

 been found out. In captivity it will eat flesh of almost any animal. It 

 does not thrive as well on beef, however, as does C. bartoni, nor does it 

 eat as much. In the cave its food must be very scanty. It certainly 

 could not catch a blind fish, and it seems scarcely likely that it would 

 ever be able to catch the relatively small and active amphipods. The 

 isopods are less active, but are very small to serve as food for so large 



