48 Mr Allan E. Grant on the 



is still " vitally active," i.e., can cause the nucleus to divide, 

 the process of indirect division can still go on, with forma- 

 tion of cell-plate. Now, as before stated, it would appear 

 from recent observations, especially those of Dr Macfarlane, 

 that it is in the nucleus and bodies contained where the 

 process of division begins, in fact that the " generative " 

 force proceeds from within outwards. The protoplasm 

 therefore would not seem to exercise any power over the 

 nucleus which causes it to divide, but rather the nucleus 

 influences the general cell-protoplasm, causing deposition 

 finally of the cell-plate. The expression, " influence of 

 the protoplasm over the nucleus" should be confined to 

 its office of nourishing the nucleus. Since then, in the 

 cells in which the multinucleated condition was observed 

 the protoplasm was still in circulation, the protoplasm 

 may, in this modified sense, be said to have still retained 

 its influence over the nucleus. It will be observed that 

 none of the observers, whose results I have summarised and 

 compared with my own, have advanced any reason for the 

 occurrence of this condition. M. Guiguard, indeed, states 

 tiiat it is not exclusively the size of the cell, but probably is 

 concerned with some physiological condition. He does not, 

 however, suggest what that condition is. Strasburger would 

 seem to be of the idea that it is of pathological significance. 

 The hypothesis advanced by Dr Macfarlane, in his 

 paper read before the Eoj'-al Society of Edinburgh,* 

 seems to be without doubt the correct one, in at all 

 events most cases, viz., that the occurrence of a plurality 

 of nuclei in cells past division is due to a continued 

 functional activity of the nucleus, more or less perfect, 

 engendered by an excess of nutrition, and by conditions 

 generally favourable to growth. It receives special sup- 

 port from the experiments of M. Prillieux when he 

 produced the condition artificially by superheating the 

 soil in which certain plants were grown. The same cause, 

 namely excess of nutrition, is, I believe, the reason of the 

 multinucleated state of the cells for the absorption of bone, 

 called osteoclasts, in the animal system, as also of those 

 large cells in the spleen which apparently disintegrate and 

 absorb the coloured corpuscles of the blood. 



* Trans. Roy. Soc Edin., vol. xxx. p. 585. 



