454 BULLETIN OF THE 



settle at the same time the nature of the share each of these nucleolar 

 structures takes in the formation of the maturation spindle. There is, 

 besides, one important point which is not, even in these studies, made 

 sufficiently clear to satisfy me. I am unable to understand how the sub- 

 stance of the nucleolus is more active in producing the stellate figures 

 than the protoplasm of the yolk. If this radial system is induced by 

 the immigration of nucleolar substance into the protoplasmic knob, then 

 certainly we should not expect the stellate figure before such immigration; 

 consequently the question must arise, What is the signification of the 

 clear non-granular spot in the protoplasmic knob ? Is it not due to the 

 same agency as that which induces the stellate figure? Is it not, in 

 fact, simply the first trace of such a figure still limited in its extent 1 

 But this clear spot antedates even that part of the metamorphosis of 

 the nucleolus by which its several vacuoles are succeeded by a single 

 larger subcentral vacuole embracing the smaller nucleolar body (compare 

 Hertwig, '77", p. 271) ; by so much the more, then, does it antedate the 

 conversion of that smaller nucleolar corpuscle into a rodlike body with 

 its end at the centre of the star. And, further, what shall be said of the 

 " langgestreckte Protoplasmaerhebungen," "which are sent out in the 

 upper wall of the germinative vesicle, raylike, from the apex of the proto- 

 plasmic knob on all sides, like mountain ridges from a central peak " ? 

 They are represented in Hertwig's Taf VI. Figs. 2 and 3, at a time when 

 the inner corpuscle is entirely enclosed in the vacuole of the nucleolus, 

 and yet the peculiar radial arrangement of these "Erhebungen" can 

 hardly be due to any other cause than that which induces the stellate 

 figure. If the first indication of the commencing metamorphosis is seen 

 in the invasion of the territory of the germinative vesicle by a protuber- 

 ance of the surrounding protoplasm, what can be the necessity of trans- 

 ferring the initiative activity to the nucleolus, which still preserves its 

 morphological integrity % May it not be that Hertwig, by his commend- 

 able exertions in rescuing the nucleus from a position of comparative 

 subordination, has ascribed to this substance undue importance, and 

 given it exclusive control where it is, after all, only one of two co-ordinate 

 factors ? A connection there doubtless is between the metamorphosis of 

 the germinative dot and the formation of a nuclear spindle, but it is not 

 so certain that the nuclear substance gives the first impetus to the forma- 

 tion of the stellate figures, which mark, in some cases at least, the first 

 unequivocal steps toward a spindle metamorphosis. When Hertwig 

 speaks of an " IJeberwanderung " of nuclear substance into the proto- 

 plasm, I understand that to imply — as in fact his figures in so precise 



