208 Proceedings of the Royal Physical Society. 



would be necessary to allow of sufficient nutrition in 

 a cell whose form of anabolism is of the unstable type. 

 Should, therefore, animals have specialised in the direction 

 of greater instability in the products of anabolism, and plants, 

 on the other hand, iu the direction of greater stability in the 

 products of anabolism, the form of anabolism in the sperm 

 would be more typical of the former, and that of the ovum of 

 the latter. There is no need to point out furtLier the antithesis 

 of maleness and femaleness as seen in the sperm and ovum, or 

 that also stamped upon the individuals which bear these 

 different forms of germ cell, as this has been fully entered 

 into by Professors Geddes and Thomson in their book on 

 " The Evolution of Sex." The comparison of the germ cells, 

 however, as differing in the nature of their anabolism, would 

 allow of the inference that the sperm is more specialised in 

 its kind of anabolism as far as the animal series is concerned, 

 while, on the contrary, the ovum is more specialised in its 

 kind of anabolism as regards the plant world. It would be 

 brought about by natural selection, as animals and plants 

 evolved further and further, through the constant selection 

 of those forms which tended to vary the most in their special 

 line of anabolism, that that sex which tended to show this 

 form of variation in the most marked degree would take the 

 lead in the process of onward evolution. This opinion, which 

 has been advocated by Eimer and others in regard to animals, 

 seems, with some exceptions, to be perfectly obvious, and 

 though among plants it is less so, it is yet a noticeable fact 

 that the female plant is more specialised than the male in 

 those forms in which the gametophyte is more or less de- 

 veloped. In the higher plants, where the asexual form has 

 become so important, in the history of the evolution of 

 degeneracy and parasitism which the gametophyte has 

 undergone, the male is perhaps somewhat in advance of 

 the female in this retrograde movement, having adopted a 

 parasitic habit of almost fungus-like nature. It might be 

 added, that in animals in which a retrograde movement is 

 seen in specialisation, the female is generally in advance of 

 the male. In considering fertilisation from the point of view 

 of a possible gain of potential by the blending of two cells 



