MUSEUM OF COMPARATIVE ZOOLOGY. 379 



method as he does. Our differences of opinion result from different 

 conceptions of the role of the nuclear substance during division, — of the 

 nature of the " Attractionsmasse," in other words. It follows from the 

 passage which I have just quoted, that he considers the two (afterwards 

 four) starch-containing masses as nuclear substance. I believe, on the 

 other hand, they are accumulations of cell protoplasm — the equivalents 

 of the so-called areas — about centres of attraction, and that the dis- 

 tance of these centres from the old nucleus is only another argument 

 tending to show what I have already suggested, that the centres of 

 attraction may perhaps at first be quite independent of nuclear sub- 

 stance. I think it will be at once apparent that from this standpoint 

 there is not so wide a gulf separating the two processes as appears from 

 Strasburger's interpretations. It no longer becomes necessary to assume, 

 with him, the existence of a new nuclear substance, to which are trans- 

 ferred the functions of the old nucleus, while the latter maintains a 

 separate existence. Nor are we forced to look upon the dissolution of 

 the old nucleus as essentially different from the metamorphosis which 

 takes place in the typical case. Barring the assumption that the cen- 

 tres of attraction are nuclear substance, the metamorphosis consists 

 essentially in the transfer of nuclear substance in two (or more) direc- 

 tions toward centres of attraction. That such a transfer of nuclear 

 substance (from the old nucleus) also takes place in these exceptional 

 cases must be granted, I think, from Strasburger's own words, for he 

 says (p. 158) : " Der Mutterzellkern wird aber inhaltsarmer, wahrend 

 seine Hautschicht dicker und granulirter erscheint (Fig. 3) ; endlich 

 schwindet er voUstandig. Es fallt dies sein Yerschw^inden mit der Zeit 



zusammen, in der die Zellplatten gebildet werden Urn dlese Zeit 



leginnt aher audi erst die Differenzirung der Zellkerne in den vier Proto- 

 plasmamassen. Die Anlage beginnt immer seitlich von der Starkemasse 

 und zwar, so weit sich dies noch sicher stellen lasst, auf derjenigen Seite, 

 welche der letzten Theilungsflache zugekehrt ist." From this I can 

 only conclude that the dissolution of the old nucleus is accompanied by 

 a transfer of its substance toward the four centres of attraction near 

 which it is employed in the formation of the four new nuclei. That 

 these new nuclei lie on that side of their respective starch-enveloping 

 masses which was last in union with a cognate mass, only serves to 

 confirm one in assuming that a part of this nuclear substance had been 

 transferred to the vicinity of the " Attractionsmasse " before the second 

 division of the latter ensued ; that assumption, moreover, seems in no 

 way to conflict with the statement that the old nucleus was at this time 



