134 



E. A. ANDREWS. 



line the groove. This made the groove more distinct than other- 

 wise is the case. The groove passes forward from the posterior 

 edge of the annulus and then bends to one side much as does the 

 bottom of the shell groove seen as a shaded line in Fig. 21. In 

 each individual, however, the amount of bending seems to be 

 different. 



Such a bent groove is very like the simple bent epidermal 

 groove of C. Clarkii, which is one of the less specialized species. 

 While previous experience had shown that larvae after living 

 eleven days in the above sixth stage might turn into a seventh 

 stage 29 mm. long in the middle of July, no observations were 

 made upon the above larvae 21 mm. long till October 3, 1904, 

 when they had turned into individuals 2553 mm - long. Those 



25-35 mm - agreed with one an- 

 other in the development of the 

 annulus and probably represented 

 larvae that from lack of enough 

 food had remained in the seventh 

 stage while the female, 53 mm. 

 long, belonged to some later 

 stage. In this laboratory it has 

 been found that crayfish of that 

 latter size have their sexual in- 

 stincts developed in the fall and 

 females 52 and 53 mm. long, being 

 x^_ then supplied with sperm by 

 males of the same or even smaller 





FIG. 23. 



sizes, laid good eggs the follow- 

 ing spring when not quite one 

 year old. Thus the above female was probably mature in instincts 

 and in external sexual organs when examined. 



First, however, taking up the specimens 25-35 mm - long which 

 were all essentially alike except in size, one 35 mm. long enlarged 

 13 diameters, Fig. 23, presents a noticeable growth of the first 

 pleopods which are now turned forward and sparsely set with 

 hairs as in the adult, and also much increase in the relative im- 

 portance of the curved ridge bounding the mouth of the oviduct 

 opening on the third leg. As an opaque object the annulus now 



