260 CRUSTACEA. 



in front of the heart, and of a median lobe extending back- 

 wards. Each lobe consists of many tubules, within which 

 the spermatozoa develop. From the junction of each of the 

 anterior lobes with the median lobe, a genital duct or vas 

 deferens is given off. This has a long coiled course, is in 

 part glandular, and ends in a short muscular portion opening 

 on the last thoracic limb. The spermatozoa are at first 

 disc-like cells, they give off on all sides long pointed 

 processes like those of a Heliozoon, and remain very 

 sluggish. The seminal fluid is milky in appearance, and 

 becomes thicker in its passage through the genital ducts. 



Fig. 109. — Female reproductive organs of crayfish. — 

 After Suckow. 



flr'., Ovaries ; 02/., fused posterior part ; od., oviduct ; int., female 

 aperture on the second walking leg. 



It is possible that the genital ducts represent modified 

 nephridia, and that the cavities of the gonads are coelomic. 



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. 



Before this, however, sexual union has occurred. The 

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



