TO THE EMBRYOLOGY OF AMPHIBIA. 27 



the ventral lip at about 80°, so that the diameter of the blasto- 

 pore occupied about 00° of the egg circumference, whereas it had 

 occupied 70° or more when it first assumed the circular shape. 



At 6 p.m., the blastopore has diminished to about 35° in 

 diameter, but the egg had become somewhat unstable, rotating 

 also when the mirror-dish was rotated, and by the next morning 

 had become utterly useless from the same reason. 



In the spring of 1900, I studied the subject under considera- 

 tion in the eggs of two other anurans {Rana japonica and Bufo 

 japonica). The spawning season of the former species about 

 Tokyo is from February to March, and of the latter species from 

 the end of March to the middle of April. 



On the morning of February 2nd, several masses of the Rana 

 eggs were obtained. From among them I fixed on the Prismen 

 Rotator an egg in the early gastrulation stage in which the dorsal 

 lip of the blastopore had already appeared and encircled about 

 one-third of the circumference. This year, I carried on my re- 

 searches in a basement room in order to have a perfectly steady 

 floor, but, although this end was attained, the temperature of the 

 room was comparatively low, and the development of the egg 

 progressed very slowly. This proved very unfortunate, as owing 

 probably to prolonged submergence the mirror became clouded, 

 until on the sixth day nothing more could be done with it. 



As the gastrulation process had been going on for sometime, 

 I could not ascertain on this egg the actual starting point of 

 the dorsal blastopore lip. Fig. 39 represents the view of the egg 

 from the lower pole at 4:30 p.m., on Feb. 2nd (the first day). 

 The right and left side-views were obtained respectively at 20° 



