76 ORGANIZATION A:'D DEVELOPMENT OF ANIMALS IS GENERAL. 



openings which are usually common to the generative organs ; they 



consist essentially of a number of coiled tubes, 

 which in the more primitive types of Vertebrates 

 have a ciliated funnel-shaped opening into the 

 t body cavity (Dogfish embryo, fig. 71). 



The individual tubules of which the verte 



GK 



FIG. 69. Longitudinal 

 section through the 

 medicinal Leech (after 

 R. Leuckart). A ali- 

 mentary canal ; 0, 

 brain ; Ok, ventral 

 chain cf ganglia ; Ex, 

 excretory canals (seg- 

 mental organs, water- 

 vascular system). 



FIG. 70. Diagrammatic representation, of 

 the segmental organs of a segmented 

 worm (after C. Semper). Da, dissepi- 

 ment ; Wtr, ciliated funnels which lead 

 into the coiled tubes. 



Lrate kidney is composed do not open directly to 

 the exterior, as do the segmental organs of 

 Annelids, but there is present on each side of 

 the body a duct, the kidney duct, which receives 

 the tubules of its own side and opens posteriorly 

 into the cloaca. They also possess an important 

 structure peculiar to the kidney of the Vertebrata 

 known as the " Malpighian body," which consists 

 of a capsular widening of the lumen of each 



