332 BULLETIN OF THE 



that the nuclei of embryonic cells and of segmentation spheres present 

 initiatory to the acts of division. 



Two communications from Giard ('76 and '77) are in so far of interest 

 here as they ascribe to Biltschli the idea that the polar globules arise in 

 the eggs of Lymnteus, Succinea, Nephelis, and Cucullanus by the pro- 

 cess of cell division ; the author then says that he is able to add that 

 the same is the case with Salmacina Dysteri, and Spirorbis ('77, p. 566). 



I do not know how the author can ascribe this idea to Biitschli, for 

 the latter seems not to have yet arrived at that conclusion when the 

 first paper (Giard, '76) was published, and gave no expression to such a 

 notion until some time after Giard's second paper had appeared. 



P. Mayer ('77, pp. 212, 213, Taf. XIII., XIV.) says that no nucleus 

 is to be found, even with the use of the ordinary reagents, in freshly 

 laid eggs of Pagurus Prideauxii, but in the course of a few hours one be- 

 comes visible. Subsequently the single nucleus has given place to two, 

 then to four, and finally to eight. It is only after the formation of eight 

 nuclei that the segmentation begins, nor are there eight cells formed at 

 once, but first two, then four, then eight. Mayer did not, on account of 

 the opacity of the eggs, observe the division of the nuclei. It is not 

 possible to say from his figures w^hether the nuclei undergo a spindle 

 metamorphsis, though the same is to be inferred, since he refers to the 

 presence of Auerbach's karyolytic figure as a matter that scarcely needs 

 to be stated. In his opinion, however, the nucleus is not dissolved, but 

 is directly divided. He has seen long-drawn nuclei and even two nuclei 

 in a cell about to divide, without thinking it necessary to conclude that 

 they are pathological conditions. 



Stossich ('77) gives an account of the nucleus during division, which 

 will be noticed elsewhere (p. 448). 



BiJTSCHLi ('77^, p. 236) states that he has, at the same time with, and 

 independently of Giard, arrived at the same conclusion touching the cell 

 nature of the polar globules, though he lays no claim to having expressed 

 that opinion in the works which were accessible to Giard when he wrote. 

 " Giard hat sich auf Grund meiner friiheren Beobachtungen diese Ansicht 

 gebildet." 



This paper of Biitschli contains no further contribution to the nature 

 of cell division and nuclear changes, save the exception which is taken 

 (p. 240) to Robin's view, — that smaller segments arise from larger ones 

 in the case of Nephelis by a budding process, in which the nucleus takes 

 no part,. Robin's position is sufficiently refuted by Biitschli's figures 

 and remarks. 



