Formation of Blastoderm 3 



later stage it is also split off from the superficial layer of yolk. 

 This outer investment therefore prevents the existence of an 

 actual passage from the cleft-like gastrula cavity to the exterior, 

 so that the archenteron is not very obvious in this class of fishes 

 at this stage. 



B 



Fig. 1. Diagram to show the growth of the blastoderm over 



the yolk. 



A, B, C, the egg as seen from above; D, E, F, the same stages seen from the side; 

 bl blastoderm ; m merocytes ; the yolk is represented by dots. 



12 



