CHAPTER II. 



The Segmentation of the Ovum and Formation 

 OF THE Layers. 



The ovum is composed of a spongework (PI. IV, fig. 13), 

 the strands of which consist of an apparently hyaline and 

 structureless material and contain a small number of highly 

 refractile globules of various, but always small, size. Glo- 

 bules of a similar nature are also found in the spaces of the 

 spongework. 



In the ovum of Peripatus Balfouri, and to a much 

 smaller extent in the ovum of P. c a p e n s i s, a number of angular 

 bodies, staining slightly deeper than the rest of the reticulum, 

 and in unstained specimens having a somewhat yellow tint, are 

 present (PI. IV, fig. 19, s.b.). At first I took these struc- 

 tures for a kind of yolk material contained in the meshes of 

 the spongework, but a more careful examination has led 

 me to believe that they are merely nodal expansions of the 

 latter ; they undoubtedly present the appearance of being 

 continued at their angles into the strands of the reticulum 

 (PI. Ill, fig. 1, s.b.). The property which they possess of 

 staining more deeply than the rest of the reticulum — a pro- 

 perty which is only visible in sections through the ovum — is 

 probably merely apparent and due to the fact of their greater 

 mass. 



There is then no yolk material in the ovum, unless these 

 bodies and the small highly refractile globules which are 

 present in very small numbers are to be regarded as such. 



The sponge-like structure of the ovum of P. capensis is very 

 conspicuous. The meshes of the spongework must be occupied 



