HOLOBLASTIC REMINISCENCE IN CESTRACION. 



39 



elusion will be lacking until the origin of the above described furrows can 

 be traced back directly into the earlier cleavages. In the mean while, 

 however, the case is so strong a one that I think we can justly refer 

 to the lines as expressing cleavage, and to the sharply outlined areas as 

 blastomeres. 



In the figures, Pl. I, Figs. A-I, are shown a series of stages illus- 

 trating characters of segmentation. The drawings* were made from the 

 living egg. It should be noted that the egg capsule, when opened from 

 either end, shows the egg with the animal pole uppermost. The egg itself 

 measures between 4 and 5 cm. in diameter: it is of semi-fluid consistency, 

 and is surrounded by a dense glairy albumen, which in turn in its outer- 

 most layer is attached to the egg capsule. The albumen is tenacious: it 

 will flow over the rim of the opened capsule, and if the escaping mass is 

 not promptly separated, it is apt to draw with it the albumen immedi- 

 ately surrounding the egg, and will thus destroy the spherical contour of 

 the yolk. Mention might also be made of a delicate whitish membrane 

 which surrounds the egg within the mass of albumen, reminding one, 

 for example, of the vitellina of Necturus. The rupture of this delicate 

 inner membrane is apt to disturb the contour of the egg. Kemoval 

 of the end of the egg capsule together with the attached albumen, 

 causes a flattening of the egg at the animal pole, more or less pronounced 

 depending upon the amount of the albumen removed. It is exceedingly 

 difficult to remove the egg from the capsule without rupturing it, 

 although in several cases I have succeeded in doing so : it sinks 

 flatly, very much as the yolk of a hen's egg. Whenever successfully 

 removed it has shortly ruptured of its own weight. In examining the 

 cleavage lines it has accordingly been found best to allow the egg to 

 remain in the opened capsule. A view of the side and vegetal pole 

 can then he had by rotating the egg by means of curved needles 

 thrust into the adjacent albumen. 



* I am indebted to Messrs. N. Yatsu and I. Kuabara for their kindness in preparing 

 them. 



