MUSEUM OF COMPARATIVE ZOOLOGY. 467 



The phenomena in Pterotrachea and Phyllirhoe are so nearly the same 

 that they are described jointly, and afford excellent results on the nature 

 of the metamorphosis. The spindle is formed within, and therefore out 

 of the substance of, the germinative vesicle. On preparations made with 

 acetic acid the spindle is found to lie through the middle of the vesicle 

 (or a little eccentric), its ends with their extensive asters lying at two 

 poles of the vesicle where its wall has been dissolved. The coagulated 

 nuclear fluid (Kernsaft) is distinguishable after the membrane of the 

 vesicle has been entirely dissolved. When the spindle has taken a radial 

 position the yolk exhibits a depression at the point where one of its ends 

 reaches the surface. The second spindle is much smaller than the first. 



While I can fully acquiesce in a majority of the points defended by 

 Blanchard (*78, pp. 747-754), I cannot think all the conclusions he has 

 reached are justified by the literature which he has so recently reviewed. 

 It is at least confusing for him to say, " The germinative vesicle disap- 

 pears, not because it is dissolved in, but because it is expelled from the 

 vitellus, just as Pouchet maintained thirty years ago," even though he 

 subsequently gives a less prejudiced account of these changes. It is 

 likewise very unsatisfactory, because incomplete, to say that the germi- 

 native vesicle in escaping from the vitellus leaves behind in the yolk 

 a part of its fluid (sue) in a state of solution. That I may not mis- 

 represent the conclusions of Blanchard, I must add that he recognizes 

 the derivation of the female pronucleus from the half of the second 

 spindle which remains in the vitellus and " se disorganised I do not 

 understand how a process of disorganization can result directly in the 

 construction of a new nucleus, and cannot share the belief that the 

 spindle metamorphosis of the germinative vesicle is " a consequence of 

 its natural death," since thereby I should be compelled to look upon 

 the spindle metamorphosis which accompanies every subsequent cell 

 division — although presenting the most striking evidence of activity — 

 as a consequence of the death of the nucleus ! One should not maintain, 

 as Blanchard does, that the polar globules exercise a considerable influ- 

 ence on the direction of the segmentation furrows and the reciprocal 

 relations of the blastomeres. It cannot be doubted that there exists a 

 constant spatial relation between the polar globules and the furrows, 

 but to seek the cause of this coincidence in a supposed influence of the 

 polar globules over the position of the furrows is to adopt an explana- 

 tion of which there has as yet been adduced no proof, and which is much 

 less satisfactory than that which makes the position of the place both 

 where the polar globules shall emerge and where segmentation shall 



