28 AKT. 3. S. IKEDA : CONTRIBUTIONS 



and 200°, and the posterior view at 290°, of the rotating dish. 

 The complete encircling of the blastopore-lips was observed at 

 2:17 p.m., on the next day, when the lips had grown down to 

 about 64° or 65° below the equator. At this time and later, up 

 to the morning of the fourth day, the gradually diminishing 

 blastoporic area was always found at the exact center of the lower 

 hemisphere (Fig. 40). At 4:05 p.m., on the fourth day, the 

 blastopore lips had grown down to 72° or 73° below the equator, 

 and the egg was just beginning its rotation as a whole. On the 

 next morning (the fifth day), the egg was found to have rotated 

 about 13° or 14° and the closure of the blastopore had also ad- 

 vanced somewhat. At 3:32 p.m., on the same day, the right side 

 view of the egg was as given in Fig. 41 : the egg had rotated so 

 that it was now resting, nearly though not yet quite, on the ventral 

 lip of the blastopore which was now reduced in diameter to f of 

 the size in Fig. 40. Further progress is seen in Fig. 42 sketched 

 at 3 p.m., on the sixth day : the egg is now resting exactly on 

 the ventral lip of the blastopore which is still further reduced in 

 size. I could unfortunately make no observation beyond this 

 point, owing as before mentioned to the clouding of the mirror, 

 but the facts brought out prove that in the main, the mode of 

 the blastopore-closure and of the egg rotation in Rana are exactly 

 like the same processes in Rhacojihorus. 



In the case of Bufo, the eggs whose development I was able 

 to follow during the breeding season of last year were only three 

 in number. Of these the third did not produce satisfactory 

 results, owing to the clouding of the mirror again. Even in the 

 case of the first two eggs which gave tolerably good results, the 

 lower view was rather imperfect from the same cause. I tried 

 therefore to supplement my observations by following three or 



