Anaholism and Specialisation. 211 



reinstate the great powers of cell division observable as the 

 results of conjugation. There would be a superiority in this 

 respect of true fertilisation over conjugation, since in the 

 latter process the differences brought into the blend would 

 be of an individual nature only, while in the former case 

 there would be superadded to this, as far as is possible in 

 each different group of animals and plants, the divergence 

 towards stability of anabolism in the ova and instability of 

 anabolism in the sperm cells. This might be pushed as far 

 as is compatible on the one hand with the retention of a 

 generalised power in the germs, and on the other hand with 

 the degree of specialisation to which evolution has carried 

 them. The sperm cell has probably throughout the animal 

 series an increasing tendency to pronounced instability of 

 anabolism, but this only to a point beyond which it cannot 

 go without losing its generalised powers. The ovum, on the 

 other hand, has acquired in different degrees in the same 

 series a much greater inclination to storage than is ever seen 

 in the ordinary conjugating forms of Protozoa, and this has 

 probably been in a large degree forced upon it by excessive 

 nutrition, causing greater stability of anabolism. In the 

 plant series the male cell is a sperm cell, except in the 

 phanerogams, where the loss of its flagellate form is probably 

 connected with the peculiar form of fertilisation, while the 

 ovum in the higher plants retains in a large degree its 

 original nature, and a high nutrition is not enforced upon it 

 until after fertilisation, as the acquirement of a form of 

 anabolism of greater stability might cause it to lose its 

 generalised power. Owing to the fact that natural selection 

 plays upon sexual individuals in animals, while in plants its 

 chief action must be upon the asexual form or sporophyte, 

 it happens that there is always more or less of a cross 

 brought about in animals through fertilisation, whereas in 

 plants this can only be obtained by elaborate mechanisms 

 to procure cross-pollenation. Seeing that plants have de- 

 veloped along static lines of evolution, and animals along 

 dynamic lines of evolution, the power of the germ cells 

 retaining their fertility would depend largely upon the 

 degree to which they retained in each their powers of in- 



