MUSEUM OF COMPARATIVE ZOOLOGY. 273 



each division of the protoplasm of the cell, and the nuclei of the daughter 

 cells arise as quite new structures; according to the other view, the 

 nucleus of the parent cell gives origin directly to the new nuclei by a 

 process of division, and the cases of supposed disappearance are to be 

 explained as resulting simply from a temporary obscuration of the 

 nucleus. 



How firmly established the former view was with botanists in 1874, 

 may be readily gathered from Sachs (Lehrbuch der Botanik, 4*^ Auf- 

 lage, Leipzig, 1874, pp. 18, 19), who expresses his doubt about the 

 division of the nucleus being in any way a general phenomenon.* 



Doubtless an equally true reflection of the views prevailing at the 

 same time among zoologists is presented by Gegenbaur ('74, p. 17) 

 when he says : " The division is introduced by a division of the nucleus, 

 and as a rule it can be established that the individual phases of the 

 division of the nucleus precede the corresponding stages of division in 

 the cell. In many cases, however, there appears to be a new formation 

 of the nucleus." 



From a comparison of these citations two conclusions can be drawn : 

 first, that in both "kingdoms," as recently as 1874, two radically differ- 

 ent methods of deportment were admitted for the nucleus ; and secondly, 

 that opinions were still at such variance as to allow very little room for 

 a parallelism between plants and animals in regard to the persistence of 

 the nucleus during cell division. 



Aside from the disappearance of the old nucleus, it was the increase 

 in the size of the new nuclei from very small beginnings, which seemed 

 to entitle the idea of complete nuclear dissolution to consideration at the 

 hands of zoologists. 



Of modes of cell formation other than by division, zoologists very gen- 

 erally accepted as well grounded a process of budding, in which the di- 

 vision of the nucleus into numerous new nuclei was followed by a 

 simultaneous constriction of the protoplasm into a corresponding num- 

 ber of parts (compare Meissner, '54", p. 262) ; but a so-called endo- 

 genous cell production — the equivalent of the "free cell formation" 

 of the botanists — has not shared with zoologists the same confidence. 



In the earlier accounts of cell division, the formation of a partition (or, 

 more commonly, the lengthening and constriction of the nucleus) was 

 observed to accomplish its division. The presence of two approximated 



* "Dass iibrigens das von Hanstein (Sitzb. der niederrhein. Gesellsch., Bonn, 

 1870) beobachtete Verhalten der Kerne nicht ganz allgemein ist, zeigeu schon die 

 Theilungsvorgange in den Antlieridien der Charen u. s. w." 



VOL. VI.— NO. 12. 18 



