288 BULLETIN OF THE 



nucleus of the first segmentation sphere. The formation of the nuclei 

 in this manner is proof to the author of the untenable position of those 

 who, like Hackel, regard such a multinuclear structure as a complex of 

 cells (p. 213). 



Biitschli's omission of all reference to radial figures about the poles of 

 the spindle is partly explainable from the transparency of the Cucul- 

 lanus eggs, which prevents the rays becoming conspicuous, and partly 

 from the great importance naturally attached to the newly discovered 

 spindle. 



Oellacher (74) has described, in a paper which T have not seen, a 

 radiate structure of the protoplasm as existing just before each act of 

 segmentation in the case of the trout. I know only so much of the 

 substance of this paper as is given by Flemming (75, p. 207), accord- 

 ing to whom, the radiate appearance is referred by Oellacher (just as 

 by Fol and Flemming) to a structural condition of the plasm, not to a 

 phenomenon of nuclear extinction. 



Flemming (75, pp. 117-128, 176 et seq. Taf. I.-IIL), on the strength 

 of renewed observations upon Anodonta and Unio together with a ro- 

 tifer (Lacinularia), in which the entire absence of a nuclear structure 

 during segmentation is maintained, accepts the views of Auerbach so far 

 as regards the dissolution of the nucleus ("der morphologische Unter- 

 gang des Kerns," p. 117), but presents numerous objections (pp. 188- 

 198) to his theory that the radiate structure is due to a distribution of 

 the nuclear sap from the tips of the nuclear cavity. He is " not yet alto- 

 gether persuaded of the Tcaryolytic nature of the radial figures " (p. 191). 



considered each of these bodies as the equivalent of a cell nucleus, and explained the 

 existence of a multiple of nuclei in each cell as a precocious activity of the nucleus, 

 whereby it anticipated by several generations the division which ultimately overtook 

 the protoplasm. Then with each segmentation half of the cluster fell to the share of 

 each of the resulting protoplasmic elements. But to explain the continued recur- 

 rence of a large number of nuclei in each cluster, even after numerous segmentations, 

 he was compelled to suppose that a process of multiplication was going on among the 

 nuclei of these clusters, so that they, as it were, kept a definite number of generations 

 ahead of the protoplasmic spheres to which they belonged, until at length, in the 

 latest stages of segmentation, this difference becoming obliterated, one could find only 

 cells with a single nucleus. However, Oellacher remains in doubt as to whether the 

 multiplication of the nuclei takes place when there are still several in the cluster, or 

 whether this only occurs when, by successive divisions of the protoplasm and corre- 

 sponding separations of the components of a cluster, the nuclei have been reduced to 

 a single one for each cell. No metamorphoses in these "nuclear clusters " were seen 

 by him, and thus the possibility of a confluence of these "nuclei" before each seg- 

 mentation was not, in that case, to be thought of. 



