CHAPTER V. 



General Considerations on the Development up to 



Stage F. 



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 convenieat 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 

 Metameric Segmentation" (No. 51). 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 the second Chapter, dealt to a certain 

 extent with the peculiarities in the segmentation of Peri- 

 patus capensis both intrinsically and in relation to other 

 forms. I think, however, that the subject is of sufficient 

 importance to deserve a more detailed treatment than it was 

 possible to give it in that place. 



There can be but little doubt that the ovum of this species 

 possessed, at a period relatively not very remote from the present^ 

 a large amount of food yolk ; that it resembled in fact in this 

 respect the ovum of the species now living in New Zealand, 

 and the ova of Arthropoda generally. The large size, 

 combined with the almost complete absence of food-yolk. 



