136 BULLETIN OF THE 



others with a single nucleus that are actually larger than the former 

 (compare the cells in Figure 14). In such cases, the single nucleus is 

 always larger than the daughter nucleus of the other cells. I am unable 

 to see that multiplication of nuclei in the cell leads to any immediate 

 increase of nuclear material. The more they divide, the smaller they 

 become. Probably the most important office of division is a more 

 extensive distribution of nnclei throughout the cytoplasm, with correspo7id- 

 ing increase of nuclear surface ; and this, considering the great superfi- 

 cial extent of the cells, and the comparatively small size of the nuclei 

 (at least in the older membranes) must be a matter of some importance 

 for the activities of the cell. It is especially so in the case of elongated 

 cells. If such cells have but a single nucleus, a large part of the 

 cytoplasm must be remote from it ; and if the nucleus is at the centre 

 of the cell, the cytoplasm at the ends of the cell will be most remote. 

 So, to restore the equilibrium between cj'toplasm and nuclei, the nucleus 

 must elongate in the longitudinal axis of the cell, and the daughter 

 nuclei move toward the ends of the cell. 



As a matter of fact, nearly all elongated cells have two nuclei, and 

 these lie in the long axis of the cell, usually rather nearer its ends than 

 to each other. It cannot be denied tliat many short or squarish cells 

 also contain two nuclei ; and, conversely, a few much elongated cells 

 can be found that have but one. In the latter case, it is interesting 

 to observe that almost invariably the nucleus has begun to elongate 

 in the longitudinal axis of the cell, and is often far advanced towards 

 division. "VVe can say almost with certainty, then, that such cells are 

 of recent formation, and that the equilibrium between cytoplasm and 

 nucleus is promptly restored by division of the latter. It is true that 

 cases like that represented in Figure 12, where nuclear division takes 

 place in the short axis of an elongated cell, cannot be explained in this 

 manner. Such instances are so rare that they might almost be con- 

 sidered as abnormal ; but the difficulty of the matter lies in the fact 

 that we get all gradations between nuclei ranged in the true longitudi- 

 nal axis, and those placed in the transverse axis. It is common to find 

 them lying more or less obliquely in the cell, though the obliquity is 

 seldom so great as to prevent them from practically fulfilling the con- 

 ditions of the hypothesis. 



It is not supposable that all the agencies impelling nuclei to divide, 

 and controlling the direction in which division shall take place, reside 

 in the cytoplasm ; possibly the most potent of them exist in the nucleus 

 itself That axial differentiation, with definite pole and antipole, is as 



