CRA YFISH. 



293 



and becomes thicker in its passage through the genital 

 ducts. It is possible that the genital ducts represent 

 modified nephridia, and that the cavities of the gonads 

 are ccelomic. 



The ovaries are like the testes, but more compact. The 

 eggs are liberated into the cavity of the organ, and pass out 

 by short thick oviducts opening on the second pair of 

 walking legs. As they are laid they seem to be coated with 

 the secretion of the cement glands of the abdomen, and the 

 mother keeps her tail bent till the eggs are glued to the 

 small swimmerets. 



FIG. 146. 



Female reproductive organs of crayfish. 

 After Suckow. 



0v., Ovaries ; 0z/., fused posterior part ; od^ oviduct ; vu. t female 

 aperture on the second walking leg. 



Before this, however, sexual union has occurred. The 

 male seizes the female with his great claws, throws her on 

 her back, and deposits the seminal fluid on the ventral 

 surface of the abdomen. The fluid flows down the canal 

 formed by his first abdominal appendages, and these seem 

 to be kept clear by the movements of the next pair, which 

 are also modified. On the abdomen of the female the 

 agglutinated spermatozoa doubtless remain until the eggs 

 are laid, when fertilisation in the strict sense is achieved. 



The Development has been very fully worked out, and is of interest 

 in being direct, without the metamorphosis so common among the 



