I 3 2 



ELEMENTARY ZOOLOGY 



taken into the mouth mixed with dirt and sand. As this 

 mixture passes through the long alimentary canal the 

 organic particles are taken up and digested. As we have 

 already seen, there are in each worm two sets of reproduc- 

 tive glands, namely, male and female organs. Each 

 earthworm produces both egg-cells and sperm-cells, but 



nephridium dorsal blood vessel 



\ hepatic cells I 

 \ \ I longitudinal muscle 



\ \ /i Circular muscle fibres 



' epidermis 

 V V ^ \ \^ ^^^cuiicle 



', ! \ nerve* cor d\ 



lephndipore ! nephrostome \ 



* D 



body cavily 



typhlosole 



ventral vessel 



FIG. 28. Cross-section of earthworm. 



the sperm-cells of one worm are not used to fertilize the 

 eggs of the individual producing them. When the eggs 

 are ready to be discharged from the bod)/, the clitellum 

 becomes very much swollen and its glands begin an active 

 secretion which hardens and forms a collar-like structure 

 about the body of the worm. As this collar moves 

 forward toward the anterior end of the body it collects the 

 eggs and also the sperm-cells previously received from 



