MUSEUM OF COMPARATIVE ZOOLOGY. 535 



its semi-solid condition, — and effect an even curvature throughout 

 its length. Such an explanation would not be inconsistent with the 

 S-shaped curves sometimes (Limax, Fig. 57) seen. But the rays show 

 a spiral tendency before they reach the periphery, and those on the side 

 of the aster nearest the surface are no more curved than those on the 

 opposite side (Fig. 66). These are obstacles which are not readily ex- 

 plainable, for it is unsatisfactory to assume that the rays extend farther 

 than they are visible. 



But whatever the view adopted regarding the cause of the spiral 

 arrangement of the rays, I believe there is great reason — both from the 

 spiral form and from the more simple deflection of the rays of the exter- 

 nal aster — for regarding them as something more than protoplasm in 

 a state of flux. It cannot be positively shown that either of the con- 

 ditions is not produced by the contracting influence of the hardening re- 

 agent until such arrangements shall have been observed in living eggs. 

 The same objections, however, hold good against considering these 

 asters artificial products, that have been so justly urged to prove that 

 asters in general cannot have been produced by reagents. Yet it still 

 remains possible to claim that the particular course of the rays in these 

 cases has been indirectly caused by the influence of the acids ; that, for 

 example, the immediate effect of the acid on the polar-globule protuber- 

 ance would be to diminish its capacity, and thereby compel the rays 

 to assume some other than the simple straight course they preserved 

 in the living state. The principal objections w^hich can at present be 

 urged against this position are, — (1.) that the surface in this (polar- 

 globule) region shows less evidence of having suffered from a contrac- 

 tion than that of any other portion of the egg, for a diminution in the 

 capacity of the protuberance would imply a folding of its envelope, but 

 that is just what does not take place; (2.) that there is a progressive 

 modification of the direction assumed by the rays, which corresponds 

 with the advancement attained in the formation of the polar-globule 

 protuberance, so that the least deflection corresponds with the least 

 advanced condition of the elevation. Besides, no reasonable diminution 

 of volume could alone account for the extensive spiral of the deeper 

 aster. I am therefore of the opinion that this phenomenon is not 

 caused by the process of hardening, and that consequently it will event- 

 ually be found in living eggs.* 



* P. S. — Prof. C. 0. Whitman of the University of Tokio, who had seen my 

 preparations previous to his departure for Japan, writes me (under date of June 18, 

 1880) concerning one of his students (Mr. lijima), engaged in studying the early 



