It shews the formation of the rudiments of the posterior nerve-roots 

 ipr) and of the vertebral rudiments ( Vr). 



Fig. 7. Section of a Torpedo embryo belonging to stage slightly later 

 than 1. Zeiss C. Ocul. 1. reduced .^. Osmic acid specimen. 



It shews (1) the formation of the anterior and posterior nerve-roots. 

 (2) The solid knob from which the segmental duct {sd) originates. 



Fig. 8. Section from the dorsal region of a Scyllium embryo belonging 

 to a stage intermediate between I and K. Zeiss C. Ocul. 1. Chromic acid 

 specimen. 



It illustrates the structure of the primitive ova, segmental tubes, noto- 

 chord, etc. 



Fig. Sa. Section from the caudal region of an embryo of the same age 

 as 8. Zeiss A. Ocul. 1. 



It shews (1) the solid oesophagus. (2) The narrow passage connecting 

 the pericardial (;9c) and body cavities {p2y). 



