MUSEUM OF COMPAEATIVE ZOOLOGY. 363 



Flemming dissents from the general views expressed by Strasburger 

 (76 and 77) as follows : — 



(1.) The nucleus is not always elongated at the beginning of division. 



(2.) It is not homogeneous before division. 



(3.) A polar opposition at two peripheral points of the nucleus is 

 formed in the " Anfangsstadien," as is shown by the grouping of the 

 "polar granules" i^ the plasma; but this polarity does not here (Sala- 

 mandra) come to the morphological expression in the nuclear mass itself, 

 which Strasburger lays down as a general principle. The poles, in these 

 animal cells, are 7iot characterized by a special refractive power. " Wdh- 

 rend die Polkbrner schon lange gruppirt sind, hesteht noch heine dicentrische 

 Ordnung in der KernfigurP There follows, rather, a radial (monocentric) 

 grouping — the star form — which finds no place in Strasburger's scheme. 

 At least, there is no visible expression of an accumulation of part of the 

 active nuclear substance at the poles, and a repulsion of another part 

 toward the equatorial plane, in this stage, nor yet in that of the forma- 

 tion of the "equatorial plate" (Flemming), inasmuch as at this time the 

 whole of the substance to become new nuclei is collected at the equator. 



I have given in some detail Flemming's views in this connection, be- 

 cause they seem to confirm in a very decided way certam of the conclu- 

 sions at which I had already arrived from the study of entirely different 

 objects, and on somewhat different grounds. It cannot fail to impress 

 one as rather remarkable that there should be no evidence of a bipolar 

 condition in the nucleus when the protoplasm was already thus distin- 

 guished, if, as has generally been believed, it is nuclear substance, which 

 constitutes the centres about which the dicentric arrangement finds ex- 

 pression. Evidently the tissue cells, which afforded the material for his 

 study, are not the most favorable objects for determining the exact posi- 

 tion of the centres about which this polar grouping of plasma granules 

 takes place. Perhaps the eggs of Limax may help to explain why this 

 early grouping ensues. I am inclined, in view of the possibility that the 

 centres of attraction may be at first phenomena of the cell plasm and 

 not of the nucleus, to suggest that these centres may also in tissue cells 

 lie totally outside the nucleus, as differentiations in the protoplasm. I 

 attach little weight to the supposed absence of a special refractive power 

 of the poles, since, for two reasons, it may have been overlooked ; namely, 



Reraak'sche Lehre von der Zelltheilung niclit zutrifFt, darauf haben Fol, ich and 

 Auerbach mit vollem Recht aufmerksam gemacht; und mit ebenso voUkommen 

 Unrecht haben wir angenommen, dass vom Kera wirklich niclits Geformtes restire, 

 well es an unseren Objecten nicht zu sehen war." 



