212 AN INTRODUCTION TO ZOOLOGY 



The principal events in the reproduction of crayfishes may be 

 enumerated as follows : 



(i) Copulation, during which the spermatozoa are transferred 

 from the vasa deferentia of the male to the seminal receptacle of 

 the female; (2) egg-laying; (3) the embryonic development 

 of the eggs; (4) hatching; (5) the growth of the young cray- 

 fishes. 



COPULATION. Copulation in crayfishes, in most cases, takes 

 place in September, October, or November of the first year of 



FIG. 109. Male crayfish transferring spermatozoa to the seminal receptacle 

 of the female. (From Andrews in Am. Nat.) 



their lives, that is, when they are about four months old. A sec- 

 ond copulating season is passed through at the end of the second 

 summer, when the animals are about seventeen months old, and a 

 third copulating season occurs at the end of the third summer 

 (179). At these times a male approaches a female, grasps her 

 by her cephalic appendages, and, after a struggle, turns her over 

 on her back. He then stands over her in the position shown in 

 Figure 109, and transfers spermatozoa to the seminal receptacle. 

 During this process, the spermatozoa flow out of the openings of 

 the vasa deferentia, pass along the grooves on the first abdominal 

 appendages of the male (Fig. 101, 14), and enter the seminal re- 

 ceptacle (159). Here they are stored during the winter. The 

 seminal receptacle is a cavity in a fold of cuticle lying between the 



