HARRIS : CRAYFISHES GENUS CAMBARDS. 167 



they would hardly find their proper place in an ecological pa- 

 per. With the frequency and time of the occurrence, how- 

 ever, we are concerned. The rate of growth and frequency of 

 exuviation in the developing Cambarus has not been so care- 

 fully observed as in Astacus, and the few notes which have been 

 made are not of a character to justify any conclusions. As to 

 the time of exuviation in older individuals we know a little 

 more. According to Putnam, a female of C. pellucidus, about 

 two and one-half inches in length, exuviated twice in a period of 

 three months, January 28 to April 20, but another specimen 

 (male or female?) of the same lot, taken in November, had 

 been kept nearly ten months without shedding. Hargitt ('90) 

 took animals of C. diogenes (?) and C. gracilis (?) which had 

 recently exuviated, and also casts in the streams only in early 

 spring. Never finding animals which had recently shed in the 

 open water, Harris ('00) concludes that individuals of C. gra- 

 cilis must exuviate in their burrows. For the observations on 

 the exuviation of C. immunis and C. virilis, see the section on 

 "Dimorphism," where it is considered in connection with the al- 

 ternation of forms. 



Breeding Habets. Data concerning the reproduction of any 

 group of animals are admitted to be of the greatest importance. 

 While observations are not extensive in the genus under con- 

 sideration some interesting points are recorded. Some of the 

 suggestions made by observers are based on such scanty data 

 that they are ignored here. 



The observations on conjugation need not be summarized here, 

 since they have been so concisely stated by Mr. Andrews, the 

 only one who has published on this subject. 



The carrying of the eggs and young by the female i:)arent need 

 not be considered in this place. 



In C. diogenes, the habits of which have attracted the atten- 

 tion of more observers than those of any other species, conju- 

 gation and the laying of eggs seem to take place in the spring. 

 Girard ('52) found the females in the burrows carrying eggs 

 in March and April. Tarr ('84) gives the middle of May as the 

 approximate time of the hatching of the eggs. Hargitt ('90) 

 observed C. ohesus and C. gracilis kept in aquaria conjugating 

 in the spring. He never found crayfishes (sp.?) mating ex- 

 cept in March, April, and sometimes May, and in only two in- 



