296 



ZOOLOGY 



gives off a vessel which supplies the head and its appendages ; 

 both the aorta and the heart also give off lateral branches, 

 which supply each segment. No antennary gland is present. 



AseUt(s, like the majority of Isopods, is dioecious. The 

 ovaries consist of two sacs, entirely independent of one another, 

 which occupy the thorax, and extend into the abdomen. A little 

 behind their middle point, in the fifth free thoracic segment, a 



! ■ ■ ? ' l ^ l \ l ? l W,.-.L^ 



Fig. 172. — Asellus aquaticus. 

 Male Tiewed from above. 

 From Leuckart and 

 Nitsche, after G. 0. Sars. 



1. Anterior antennae. 



2. Posterior antennae. 

 3-9. Thoracic limbs. 



10. The last pair of abdom- 



inal limbs. 



11. Testes Tvith their efferent 



canals. 



The nervous system is shovra 

 black. 



short oviduct descends from the ovary, and opens on the sternum 

 of that segment ; this oviduct seems also to function as a recep- 

 taculum ovorum; at their exit the ova pass into the brood- 

 pouch formed by oval lamelUform processes (oostegites) borne 

 by each of the four pairs of anterior walking limbs. 



