STRUCTURE OF CRAYFISH 



333 



are three-lobed, and communicate with the exterior by 

 paired ducts. 



The testes consist of two anterior lobes lying beneath 

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

 backwards. 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 sperma- 



FiG. 177. — Female reproductive organs of crayfish. — 



After Suckow. 



ov.. Ovaries ; ov'., fused posterior part ; od., oviduct ; vu., female 

 aperture on the second walking leg. 



tozoa are at first disc-like cells ; they give off on all sides 

 long pointed processes like those of a Heliozoon, and re- 

 main very sluggish. The seminal fluid is milky in appear- 

 ance, 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 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 



