THE ASCIDIANS AND AMPHIOXUS 



107 



J Figure 7.1 



The development of the Ascidian Styela. 

 {a) Before fertiUsation, showing the large germinal vesicle(^.t^.) and the peri- 

 pheral yellowish layer (y), and the inner grey yolky cytoplasm. 

 {b) Immediately after fertilisation. The germinal vesicle has ruptured and 



