DEVELOPMENT OF SPELERPES BILINEATUS 



231 



the B mark was visible. The A and C marks had spread some- 

 what. 6:40 P.M. (fig. 76), the A mark had extended into a band, 

 reaching the left side of the blastopore. The C mark appeared 

 drawn out towards the right, showing a movement of the blasto- 

 pore clock-wise. Next morning (fig. 77) the marks had faded 

 considerably and both A and C now lay above the blastopore, 

 which had an extension on the right side. 



A close study of the eggs marked about the equator show, in 



72 



73 



Figs. 69-73 



many cases, similar movements of the blastopore, especially 

 when only the ends of the marks nearest the blastopore are con- 

 sidered (figs. 48-63). 



It is impossible at present with the meager data at hand, to 

 discuss these movements. All we can say is that they are con- 

 cerned with the movements of cells into the egg, during the proc- 

 ess of gastrulation, and that they are also concerned with the 

 formation of the neural folds. I am inclined to believe that 

 they represent a specialized process of gastrulation, though 

 Eycleshymer notes that the blastopore of Amblystoma does not 

 always extend symmetrically. It is quite evident from my 

 observations that the movements of cells are not equally fast on 



