MUSEUM OF COMPAEATIVE ZOOLOGY. 325 



uomena with such freedom of interpretation that one is constantly 

 meeting with surprises. He has maintained, as above stated, that the 

 nucleus becomes fused with the surrounding protoplasm, but now claims 

 (p. 138) that its disappearance is not caused by a veritable dissolution 

 and mixing of its substance with this protoplasm, but that it is due 

 rather to a molecular change which renders it optically like the proto- 

 plasm, but without dispersion of its elements; and presently (p. 139), 

 when speaking of Biitschli's opinions, he says : " Je crois volontiers que 

 le nucleus se partage en deux et que cette division est visible chez les 

 vers." 



It appears to me another question whether, in its division, the nucleus 

 has an active role. Certainly there is much to show that the activity is 

 not all on its part. As the author justly remarks, it cannot serve as the 

 centre of attraction presiding over the division of the cell, since the cen- 

 tres of attraction originate at the boundary of the nucleus and proto- 

 plasm. Although I cannot unreservedly subscribe to the belief that the 

 successive modifications of the nucleus take place in a manner ^' tout * 

 a fait passive " for it, it is much easier to indorse the statement that 

 the nucleus deports itself in a manner quite as passive as the rest of 

 the cell. 



Fol's writings up to this time teach unequivocally that the new nuclei 

 arise at the centre of the radial structures of the protoplasm ; it is there- 

 fore surprising that the author now expresses his assent to Auerbach's 

 discovery,* as though there were no fundamental difference between them 

 to be explained, and then calls attention to the grave error of Strasburger, 

 who mistook the protoplasmic mass (area) surrounding the centres of 

 attraction for the nuclei. 



Biitschli's spindle fibres are, in Fol's opinion, filaments of sarcode ; the 

 granules (of the nuclear plates) are varicosities of the filaments, which 

 have no relation whatever with the nucleoli, f 



Fol states, a little farther on, that the substance of the old nucleus 

 appears to contribute to the formation of the new nuclei. 



Stossich ('76) has observed the radial arrangement of the protoplasm 



* " Du reste, Auerbach a remarque avec justesse que les deux taches claires qui 

 paraissent representer le nucleus divise et momentaremeiit modifie, reparaissent dans 

 une position excentrique et se rapprochent ensuite du centre de chacune des deux 

 etoiles moleculaires." 



t The author seems to have made a slight mistake in stating (p. 141) that Biit- 

 schli's first accurate description of the spindle and its fibres is to be found in his 

 communication in the July (1875) Heft of the Zeitschr. f. w. Zool. A very good 

 description will be found in the March number of that periodical, p. 208. 



