The Origin of Species 303 



cells and the methods of fertilization, and this is 

 also true of the evolution of the nuclei of the body 

 cells. These resemblances are all the more wonder- 

 ful, as it is difficult to see how one type could have 

 been inherited directly from the other. At the 

 time when plants and animals definitely parted com- 

 pany, sexuality was either not developed at all or 

 was on a very low plane, and consisted in the sim- 

 ple fusion of two similar gametes or sometimes of 

 two complete individuals. Moreover, the nuclei of 

 these primitive organisms, such as the Flagellata, 

 do not seem to possess the complexity of structure 

 found in the nuclei of the higher plants and ani- 

 mals. Since the sexual elements of the higher plants 

 and animals are independent developments, it is 

 probable, in spite of the close resemblances, that 

 there are inherent differences in their nature, cor- 

 responding to the differences existing in the bodies 

 of plants and animals, and it is not likely that the 

 laws governing the development of one will apply 

 without exception to the other. We may, for in- 

 stance, show that the early segregation of the sexual 

 elements in many animals justifies the assumption 

 of a special germ plasm ; but if we try to apply this 

 hypothesis to plants, it breaks down completely, as 

 it is quite impossible to cite any evidence for such 

 segregation of sexual cells in these organisms, which 

 in very many cases do not arise from sexual cells 

 at all and may be asexual throughout their whole 

 existence. 



