106 NATURE STUDY REVIEW [8 :3— Mar., 1912 



them to too much Hght when they are first brought in, and direct 

 sunUght must be avoided. 



There is something fascinating to all of us in watching ani- 

 mals eat. In a zoo the most popular hour is the one when the 

 food is distributed. Crayfish when brought into the laboratory 

 usually refuse food the first few days. Soon, however, an earth- 

 worm dangling before them is seized greedily and eaten on the 

 spot. Aquatic plants, earthworms, small crustaceans from the 

 same stream as the crayfish, bits of fresh meat, bread, cracker — in 

 fact, almost anything is taken readily. A varied diet is best. Two 

 or three times a week is often enough to feed them, perhaps too 

 often if they are in a cool place. As soon as they have all stopped 

 eating the water should be changed in order to remove all parti- 

 cles of food and prevent decay. The aquatic plants will have to 

 be renewed often, as the crayfish eat them greedily. However, 

 they are not necessary although advisable. 



Crayfish have one deplorable habit — that of cannibalism. 

 However, it is a question whether the blame should not rest 

 upon the careless person who lets them go hungry. Yet even 

 when they seem well fed, if little ones and big ones are kept in the 

 same jar, castastrophes of this sort are very common. 



The seasonal life history is not the same for all species, the 

 breeding seasons differing in different species. The rocky brook 

 crayfish (C. propinqnis) lay their eggs in the sjM-ing, but the small 

 crayfish found in the autumn and winter in the mud bottomed 

 streams are probably from autumn broods of other species. The 

 egg laying of this species may be expected in March, and for the 

 benefit of those who may not have Professor E. A. Andrews' 

 article at hand I venture to quote his description of the 

 phenomena. 



"In March the females may be put into dishes of running 

 water by themselves, one. or but few, in each dish. The indica- 

 tion that a female Cambarus is likely to lay eggs is that the 

 annulus ventralis shows a white speck or plug projecting from 

 its orifice. And such a female will predict the time it is going 

 to lay by a most noteworthy process of cleansing that goes on 

 several days before the eggs are laid and which should be care- 

 fully studied as a ])urposeful instinct. 



"The female about to lay should, preferably, be kept little 

 disturbed and with one corner of the dish screened to give shade. 



"The actual laying will, with rare exceptions, take place in 

 the night, and the next morning the pupils may dimly see some 

 hundred of eggs held enclosed in a mass of nmcus inider the 



