364 BULLETIN OF THE 



the unfavorable nature of his objects for determining the exact position of 

 the centres of attraction, — for the granules are very scanty and of com- 

 paratively large size, — and the fact that he was especially interested in 

 a confirmation (or negation) of Strasburger's view, whereby his attention 

 was directed to an accumulation of active " JTenzstoff" in this vicinity. 



The evidence to be gathered from Flemming's paper as to the exact 

 condition of the nuclear membrane "when these polar figures of the proto- 

 plasm first appear, is not absolutely decisive in favor of the view that the 

 centres of attraction are formed quite independently of nuclear substance, 

 although his own conclusions are positive {loc. cit., p. 364) in excluding 

 the possibility of a mingling of nuclear mass and protoplasm at this 

 stage.* The fact that the dicentric arrangement in the protoplasm is not 

 shown on the figures of stained preparations (except at a much later stage) 

 makes it the more difficult to form a just idea of the temporal relation 

 of these two series of phenomena, — the plasmic and the nuclear. How- 

 ever, Flemming assures us (in the explanation of the plates) that the 

 stage reproduced in Taf. XVI. Fig. 2 a (where the appearance of the di- 

 centric arrangement is first figured) corresponds to the stained specimen 

 (Taf. XVII. Fig. 3) to which the description just pointed out refers. 

 This seems to indicate the same conclusion as must be drawn from Fig. 

 62 of Limax, where the nuclear membranes of both pronuclei are still 

 intact, sharply defined, douhle-contoured structures, and where one of the 

 polar stars has already made its appearance. It is certainly difficult to 

 conceive how 2a\y formed substance could, in this case, have come to 

 occupy such a position outside the nuclear membrane. I cite this figure 

 for two reasons : the egg was hardened in chromic acid (not in acetic 

 acid, which has been thought to produce an artificial appearance of the 

 nuclear membrane), and the sections were all preserved, so that I can 

 say with positiveness that only one stellar figure was recognizable in 

 this case. This is of importance in showing a closer approximation to 

 the first appearance of the stellar figure than most other observers have 

 made, and therefore serves to justify my conviction that their conclu- 

 sions may, at least in some cases, rest upon insufficient observations. 



* " Dagegen besteht noch jetzt eine scharfe Abgrenzung der Kernfigureii gegen das 

 Plasma, allerdings nur an gefarbten Objecten (Taf. XVII. Fig. 3) sicher zu stellen 

 als ein feiner, aber scharfer Contour. Derselbe kann aber mit der alten Kernmem- 

 bran nicht mehr identisch genannt werden, denn er ist zarter und nicht immer so deut- 

 lich, wie sie, tingirbar ; vielleicht ist er ein Rest von ihr, vielleicht nur der Ausdruck 

 der Grenze zwischen Kernmasse und Plasma, — aher es ist Gewicht daraufzu legen, 

 dass diese Grenze auch noch in diesem Stadium eine scharfe, eine Vermischung von 

 Kernmasse und Plasma also fur dasselbe noch jedenf alls auszuschliessen ist." 



