256 DARWINISM AND THE PROBLEMS OF LIFE 



formed in the same way from the spermatozoon. The 

 fact that the latter is much smaller and differently 

 shaped from the former is due to an adaptation which 

 we shall deal with later. This distinction only appeared 

 when it was no longer possible for the ovum or 

 spermatozoon alone to develop into a new animal, and 

 a conjunction of the two was needed. The blending of 

 the two germ-cells, the spermatozoon and the ovum, is 

 called amphimixis .* 



It was the introduction of this into the organic world 

 that deprived the two germ-cells of their independence ; 

 from that time there could be no reproduction without 

 union of the sperm-cells and ova. 



As a matter of fact, amphimixis provides the start in 

 the formation of new individuals in the case of most 

 animals. But this is only its subsidiary purport, and 

 not the ground of its introduction, since the germ-cells 

 can grow into new individuals without amphimixis, as 

 we see in the daphnidae and phylloxeras. Its chief 

 significance is that before a new individual is formed 

 the characteristics of two animals must be blended. 

 The qualities of the father are contributed by the 

 spermatozoon : those of the mother by the ovum. 

 Thus the new individual has a selection of paternal 

 and maternal traits and of the ancestors on either side. 

 The nose, for instance, may follow that of the father, 

 or of the mother, or of any ancestor. How it is that 



1 Weismann has shown that amphimixis (a name he has himself 

 invented) has originally nothing to do with propagation. It was he 

 who first adduced the parthenogenetic animals in proof of this con- 

 ception, and we shall generally follow him in our further observations 

 on amphimixis. 



