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 

 sequence 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 the 

 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 



