312 NATURAL SCIENCE [May 



sudden increase of nutrition while gamogenesis is being thus initiated, 

 causes resumption of agamogenesis, shows that the gamogenesis is 

 consequent upon the failing agamogenesis. See then the parallel. 

 On going back from multicellular organisms to unicellular organisms 

 (or those homologues of them which form the reproductive agents in 

 multicellular organisms), we find the same law hold. The polar 

 bodies are aborted cells, indicating that asexual multiplication can 

 no longer go on, and that the conditions leading to sexual multipli- 

 cation have arisen. If this be so, decrease in the chromatin becomes 

 an initial cause of the change instead of an accompanying incident ; 

 and we need no longer assume that a quantity of precious matter is 

 lost, not by passive incapacity, but by active expulsion. Another 

 anomaly disappears. If from tlie germ-cell there takes place this 

 extrusion of superfluous chromatin, the implication would seem to be 

 that a parallel extrusion takes place from the sperm-cell. But this 

 is not true. In the sperm-cell there occurs just that failure in the 

 production of chromatin which, according to the hypothesis above 

 sketched out, is to be expected ; for, in the process of cell-multiplica- 

 tion, the cells which become spermatozoa are left with half the num- 

 ber of chromosomes possessed by preceding cells : there is actually 

 that impoverishment and declining vigour here suggested as the 

 antecedent of fertilisation. It needs only to imagine the ovum and 

 the polar body to be alike in size, to see the parallelism; and to see 

 that obscuration of it arises simply from the accumulation of cyto- 

 plasm in the ovum. Herbert Spencer. 



