DEVELOPMENT OF THE CAPE SPECIES OP PERIPATUS. 515 



baud, they never open between a pair of fully-developed legs, 

 but always behind the last pair of such ; the legs correspond- 

 ing to the generative nephridia being more or less completely 

 rudimentary (anal papillae, &c.); and it seems to me not un- 

 reasonable to suppose that this abortion of the appendage has 

 carried with it the abortion or non-development of the portion 

 of the somite which, in the preceding legs, gives rise to the 

 internal vesicle of the nephridia. 



It would be of interest in this connection to observe 

 whether the oviduct of the New Zealand species, in which 

 the generative ducts open between a pair of fully-developed 

 legs, possesses a structure corresponding to the receptaculum 

 ovorum. 



There are rudiments of two pairs of somites behind the 

 somites of the anal papillse in Stage e. One of these is just 

 visible in Stage f. They vanish completely at the end of 

 Stage F. No appendages or rudiments of such are developed 

 in connection with them. 



General Considerations. 



There are four points in the development of Peripatus 

 capensis which appear to me to deserve a more detailed con- 

 sideration and comparison, with corresponding processes in 

 other types, than it is convenient to give them in a descriptive 

 account. These are : (1) The incomplete segmentation, and 

 syncytial nature of the embryo ; (2) the development of the 

 mesoderm; (3) the development of the vascular system, body 

 cavity and coelom ; and (4) the relation of the blastopore to 

 the mouth and anus. 



The last point has already been sufficiently considered and 

 its significance pointed out in my paper " Ou the Origin of 

 Metaraeric Segmentation" (No. 32). I see no reason to 

 modify the views there set forth on this subject; on the con- 

 trary, recent investigations seem to give them additional 

 support. 



(1) I have already, in Part II of this series, dealt to 



