240 HUBERT DANA GOODALE 



7. The blastopore never extends beyond a half circle. There 

 is no ventral lip and consequently no yolk plug. The blastopore 

 closes by shortening and becomes the anus. 



8. No neurenteric canal was found. 



9. The neural folds form and close much as in Triton. 



10. The neural groove is not the seam of closure of the blasto- 

 pore lips, neither is it entirely the result of inequalities in rate 

 of growth, nor is it the priinitive streak. Its significance appears 

 wholl}' unknown. 



11. Gastrulation takes place by active invagination of the 

 yolk cells on both sides of the blastopore. The amount of invagi- 

 nation is greatest below the lip. Pari passu with this invagi- 

 nation, the yolk cells of the Rand zone spread over the ventral 

 surface of the egg. 



12. The roof of the archenteron is derived exclusively from 

 yolk (vegetative) cells. Its posterior part is from yolk cells 

 which lay above the lip of the blastopore and which have been 

 invaginated. It is not clear whether the remainder of the roof 

 has arisen from yolk cells which previously formed the floor of 

 the blastocoele, or whether thej' have arisen from the outer 

 yolk cells by invagination. 



13. The gastral mesoderm arises by delamination in situ from 

 the yolk cells forming the roof of the archenteron. The peri- 

 stomial mesoderm likewise arises from the yolk cells, which in 

 part lay at the lower corners of the blastocoele. 



14. The notochord differentiates from the yolk cells lying in 

 the dorsal midline of the archenteron roof. 



15. Blue spots may be produced upon the living egg by means 

 of Nile blue sulphate. These spots enable a determination to 

 be made of the relation of various parts of the egg to the future 

 embryo, 



16. No constant relation was found between the planes of 

 cleavage and the planes of the embryo. 



17. The head of the embryo develops near the upper pole of 

 the egg. Its tail appears somewhat above the lower pole. The 

 embryo is usuallj^ 180° long when it first appears. 



