9OO ANATOMY AND DEVELOPMENT 



part of it is surrounded by a peculiar cellular tissue, probably, as 

 suggested by Moseley, equivalent to the fat bodies of insects. 

 It is continued from close to the hind end of the body to the 

 head, and is at its maximum behind. In addition to this vessel 

 there is present a very delicate ventral vessel, by no means easy 

 to see, situated between the cutis and the outer layer of circular 

 muscles. 



SEGMENTAL ORGANS. 



A series of glandular organs are found in Peripatus which 

 have their external openings situated on the ventral surface of a 

 certain number of the legs, and which, to the best of my belief, 

 end internally by opening into the lateral compartments of the 

 body-cavity. These organs are probably of an excretory nature, 

 and I consider them homologous with the nephridia or seg- 

 mental organs of the Chaetopoda. 



In Peripatus capensis they are present in all the legs. In all 

 of them (except the first three) the following parts may be 

 recognized : 



(1) A vesicular portion opening to the exterior by a narrow 

 passage. 



(2) A coiled portion, which is again subdivided into several 

 sections. 



(3) A terminal section ending by a somewhat enlarged open- 

 ing into the lateral compartment of the body-cavity. 



The last twelve pairs of these organs are all constructed in a 

 very similar manner, while the two pairs situated in the fourth 

 and fifth pairs of legs are considerably larger than those behind, 

 and are in some respects very differently constituted. 



It will be convenient to commence with one of the hinder 

 nephridia. Such a nephridium from the ninth pair of legs is 

 represented in fig. 28. The external opening is placed at the 

 outer end of a transverse groove placed at the base of one of the 

 feet, while the main portion of the organ lies in the body-cavity 

 in the base of the leg, and extends into the trunk to about the 

 level of the outer edge of the nerv.e-cord of its side. The ex- 

 ternal opening (p s) leads into a narrow tube (s d\ which 

 gradually dilates into a large sack (s). 



