^•. 



EFFECTS OF AMPHIMIXIS ON ONTOGENY 25/ 



with all its constituent determinants^ or only a portion of it, is 

 passed into the germ-cell which will give rise to a new individual ; 

 and also what proportion of it is constituted by the gerni-piasni 

 of the grandparents, great grandparents, and more re/note ances- 

 tors. The fact that the reducing division, which takes place 

 both in the male and female germ-ceils before fertilisation, 

 removes half of the idants from each, leads us to conclude 

 that only half the normal nu tuber of ids can be contained in 

 each germ-cell •, and this could only be the case if two of each 

 kind of parental idant were present in the germ-plasm, and 

 if the reduction resulted in each individual germ-cell containing 

 a similar group of idants. But this cannot be so, for the germ- 

 plasm must consist of a number of entirely different idants, 

 unless, in consequence of interbreeding, two of the same kind 

 are present in certain of the groups. The whole of the idants 

 of both parents evidently cannot possibly be contained in any one 

 germ-cell, because the total number would be twice as great as 

 that which actually occurs in a ripe germ-cell. If in Man, for 

 example, there were thirty-two idants in the fertilised ovum, 

 sixteen of them would be derived from each parent. Of this 

 latter number, sixteen at most could be derived from one grand- 

 parent, and this could only occur if no idants at all from the 

 other grandparent had passed into the germ-cell in question. 

 It is evidently more than inaccurate to lix the limit of the he- 

 reditary power — as is done by animal-breeders — of a parent at 

 \, of a grandparent at \, of a great-grandparent at \, and so 

 on.* These numbers do not even represent the maximum or 

 minimum share in heredity which may be taken by the respec- 

 tive ancestor in the constitution of the fertilised ^g^- The 



* Galton has also emphasised this fact in the concluding chapter of his 

 book on 'Natural Inheritance' (p. 187 et seq.). According to his view, 

 the ' personal heritage ' of each parent = \, and the heritage of ' latent 

 elements ' of the parent likewise = 4, the two together thus making up \. 

 Naturally I cannot agree with this calculation, for in my opinion the 

 latency of the characters of a parent does not result from the ' primary 

 constituents ' of these qualities, but from the struggle between the primary 

 constituents of both parents ; and I do not in the least suppose that the 

 primary constituents which practically give rise to the individual become 

 separated from those which form the latent germ for the germ-cells of the 

 next generation. But I fully agree with Galton that all the 'characters' 

 of the ancestor — the grandparent, for instance — are never present in every 

 germ-cell from which a grandchild may arise. 



