MUSEUM OF COMPARATIVE ZOOLOGY. 365 



Flemming finds in his studies nothing to homologize with the "Kern- 

 spindel," and therefore concludes that division may take place in the 

 cells of animal tissues without such a structure. In Triton and Sala- 

 mandra nothing of the interzonal filaments (Kernfaden, Strasburger) or 

 the cell plate has been discovered. So, too, the thick fibres which Stras- 

 burger calls in Nothoscordum fragrans " Kernspindel " are really homolo- 

 gous to the whole stainable nuclear figure, and are therefore comparable 

 with '' Kernplattehelemente " rather than the spindle. 



In view of Peremeschko's statement that in Triton there are equato- 

 rial thickenings in the cask-shaped structure, and of Schleicher's recog- 

 nition of interzonal filaments, these conclusions of Flemming are less 

 convincing. One may still entertain a doubt if, after all, we should not 

 recognize in some of the stages seen by Flemming (e. g. Taf. XVII. 

 Fig. 14) the equivalent of spindle and nuclear plate combined. 



Flemming emphasizes the fact that the stellate or monocentric condi- 

 tion of the nuclear substance is not to be confounded with a stellate 

 figure of the cell plasm, and yet that the two are so similar that it would 

 seem extremely improbable that they were such merely by chance. He 

 says , " It seems to me hardly deniable that the yolk radiations as well 

 as the stars represent a visible expression of the forces which at that 

 particular time are active in the cell substance and nuclear substance, 

 and which operate according to a moTzocentric-radial type before the di- 

 vision, a c?2-*centric-radial type after the division." {loc. dt., p. 422.) 



It does not seem to me that his ow^n observations justify a conclusion 

 which makes the forces eff'ecting both these conditions identical, and the 

 figures themselves the successive expressions of the same continuous 'force. 

 Viewing the cell as a whole, they are not simply successive phenomena ; 

 they are co-existing. The changes in the nuclear substance lead from the 

 monocentric to the dicentric condition, and so far there is a succession, 

 in the manner suggested ; but with the cell as a whole it seems much 

 more as though there were two distinct (though analogous) and in a sense 

 ; antagonistic forces, — one acting from the centre of the nuclear substance 

 ' and finding expression in the monocentric condition of the same ; the 

 i other acting from the stellar poles in the cell plasm and ultimately domi- 

 nating, till, with the effected division, the first or nuclear force is en- 

 abled to reassert its supremacy. In this connection I must repeat what 

 has been so many times said, that the centre of the new nucleus (the 

 seat of the nuclear force) is not identical in position with the centre from 

 . which the forces of the cell plasm operate. It is possible that this hy- 

 pothesis may account for the oscillations (systole and diastole) observed 



