Fic. 6. 
NTGaSs 
Fre. 10. 
ite, 2 
Sagittal sections of early and late gastrule of Ganoids and Teleosts. 6, 7. 
Lepidosteus. (In Fig. 7 the blastopore has just closed.) 8,9. Acipenser. 
10, 11. Amia. 12, 13. Teleost. c. Coelenteron. px. Dorsal lip of blasto- 
pore. H. Head (= cephalic thickening of neuron). 1. Inner germ layer. 
Kv. Kupffer’s vesicle. m. Middle germ layer. m’. Merocytes (= periblast 
in Fig. 12). 0. outer germ layer. sc. Segmentation cavity, y. Yolk 
region, yp. Yolk plug, 
