316 BULLETIN OF THE 



ment, that an elongation of the blastomere itself has taken place in the 

 direction of the axis of the spindle ; and 



(3.) That both spindles have the same thickness at the middle, (the 

 apparent thickness being unchanged by the supposed obliquity,) which 

 would not be expected if the spindles differed considerably in size. 



Although the observations made on Limax add another case to those 

 where the stellate figures certainly arise before the disappearance of the 

 nucleus, I think it will be difficult to show any case which shall justify 

 the conclusions drawn by Bobretzky from his studies on the origin of 

 the spindle -, certainly his own figures do not warrant him in saying : 

 " Obschon der Kern wenigstens in seiner ausseren Form noch unveran- 

 dert erscheint, kann man schon hier den sogenannten spindelformigen 

 Korper unterscheiden, dessen Entstehung also keineswegs auf eine Um- 

 wandlung des Kerns zuriickzufiihren ist." 



I must especially insist upon the insufficiency of Bobretzky's observa- 

 tions to establish this assertion. The statement is evidently based on 

 such stages as those shown in Figs. 24 and 29. n. I have given above 

 what seems to me a more reasonable interpretation of his Fig. 24, and 

 have only to add that Fig. 29. n, although showing at the same time 

 the nucleus with a nucleolus and the two stellate figures, does not ex- 

 hibit the least trace of interstellate rays, — a spindle, — so that it 

 does not affi^rd any ground for the assertion, that " the origin of the 

 spindle-shaped body is in no way referable to a metamorphosis of the 

 nucleus." 



Eespecting the new nuclei, Bobretzky states, that they are to be dis- 

 covered as small bodies connected by fine granular lines as soon as the 

 segmentation furrow, which is to separate their respective cells, makes 

 its appearance (Fig. 25); that subsequently the nuclei have become larger 

 and the nuclear commissure has become almost invisible (Fig. 26). Ac- 

 cording to this latter figure the commissure is more conspicuous in the 

 middle than near the nuclei, just as I have found it to be in Limax, ex- 

 cept that the striate appearance is not at all represented in Bobretzky's 

 figures. 



Of the method in which the nuclei are formed, the author is not able 

 to say anything very definite. In the stages just mentioned, he believes 

 he has seen in the clear central spot of the stars an accumulation of very 

 small pale vesicles, from which one might deduce the formation of new 

 nuclei. No reconciliation of this untenable assumption with the accurate 

 observation recorded in the following sentence is attempted. Bobretzky 

 saw, namely, in one case clearly (Fig. 29 ^. m) two new nuclei in addi- 



