GENESIS. 223 



absorbed or dissipated, while the ovule aborts ; and the un- 

 impregnated ovum eventually decomposes. 



Such being the characters of these cells, and such being 

 their fates if kept apart, we have now to observe what hap 

 pens when they are united. For a long time, the immediate 

 aequence of their contact was not ascertained. This is at 

 length, however, decided. It has been shown that in plants, 

 the extremity of the elongated pollen-cell applies itself to tho 

 surface of the embryo-sac, but does not enter the embryo- 

 sac. In animals, however, the process is different. Careful 

 observers agree, that the spermatozoon passes through the 

 limiting membrane of the ovum. The result in both cases is 

 presumed to be a mixture of the contents of the two 

 cells. The evidence goes to show that in plants, matter 

 passes by osmose from the pollen-cell into the embryo- 

 cell ; and that in animals, the substance contained in the 

 spermatozoon becomes mingled with the substance contained 

 in the ovum, either by simple diffusion or by cell-multiplica 

 tion. But the important fact which it chiefly con 

 cerns us to notice, is, that on the union of these reproductive 

 elements, there begins, either at once or on the return of 

 favourable conditions, a new series of developmental changes. 

 The state of equilibrium at which each of them had arrived, 

 is destroyed by their mutual influence ; and the constructive 

 changes which had come to a close, recommence : a process 

 of cell-multiplication is set up ; and the resulting cells pre 

 sently begin to aggregate into the rudiment of a new 

 organism. 



Thus, passing over the variable concomitants of gamo 

 genesis, and confining our attention to what is constant in it, 

 we see : that there is habitually, if not universally, a fusion 

 of two portions of organic substance, which are either them 

 selves distinct individuals, or are thrown off by distinct 

 individuals ; that these portions of organic substance, which 

 are severally distinguished by their low degree of special 

 ization, have arrived at states of structural quiescence or 



