244 PEOFESSOR F. M. BALFOUR. 



Segmental Organs. 



A series of glandulai* 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 Chsetopoda. 



In Peripatus capensis they are present in all the legs. 

 In all of them (except the first three) the following parts may 

 be recognised : 



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 opening 

 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 nerve-cord of its side. The ex- 

 ternal opening (o s) leads into a narrow tube (s d), which 

 gradually dilates into a large sac (s). 



The narrow part is lined by small epithelial cells, which are 

 directly continuous with and perfectly similar to those of the 

 epidermis (fig. 20). It is provided with a superficial coating 

 of longitudinal muscular fibres, which thins out where it passes 

 over the sac, along which it only extends for a short distance. 



The sac itself, which forms a kind of bladder or collecting 



