XL] EVOLUTION IN BIOLOGY. 289 



of living precipitate. We now know, on the contrary, 

 that the female germ or ovum, in all the higher 

 animals and plants, is a body which possesses the 

 structure of a nucleated cell; that impregnation 

 consists in the fusion of the substance 1 of another 

 more or less modified nucleated cell, the male 

 germ, with the ovum ; and that the structural 

 components of the body of the embryo are all 

 derived, by a process of division, from the coalesced 

 male and female germs. Hence it is conceivable, and 

 indeed probable, that every part of the adult contains 

 molecules, derived both from the male and from the 

 female parent; and that, regarded as a mass of 

 molecules, the entire organism may be compared to a 

 web of which the warp is derived from the female 

 and the woof from the male. And each of these may 

 constitute one individuality, in the same sense as the 

 whole organism is one individual, although the matter 

 of the organism has been constantly changing. The 

 primitive male and female molecules may play the 

 part of Buffon's " moules organiques," and mould the 

 assimilated nutriment, each according to its own type, 

 into innumerable new molecules. From this point of 

 view the process, which, in its superficial aspect, is 

 epigenesis, appears in essence, to be evolution, in the 

 modified sense adopted in Bonnet's later writings; 

 and development is merely the expansion of a poten- 

 tial organism or " original preformation " according 

 to fixed laws. 



1 Not yet actually demonstrated in the case of pha3nogamous plants. 



U 



