The determination of sex in animal development. 755 



That is to say, in the "grand-child-generation" we revert to the 

 original condition. Whatever basis of truth there be in this conclusion, 

 it is none the less of interest, because from other considerations there 

 are reasons for attaching more importance to the grandparental con- 

 ditions than to the parental ones. 



For the present the above may be regarded as a "Selbstgespräch", 

 and it is merely intended to show how out of simple beginnings pre- 

 sent conditions could conceivably have been derived. But, in fact, 

 matters are complicated by two things, 1) the non-functional nature 

 of the second form of spermatozoon, in most cases at any rate, and 

 2) the fact, that reduction is now usually not merely an undoing of 

 the previous union, for female traits may be handed over to the 

 male- egg etc. 



The mingling of characters, due to the union of egg and sperm, 

 termed by Weismann "amphimixis", is to all appearance only com- 

 plete for the embryo, which thereafter arises, and, strictly speaking, 

 not for the primary germ-cells of the latter. As already recorded, 

 these retain their nuclear duplication, as long as they are primary 

 germ-cells : they could make the mingling more complete, were they to 

 develop like the embryo. But with their division into secondary germ- 

 cells they initiate the reduction. Were this a halving in Galton's 

 sense, then all the consequences drawn by him might follow. But 

 it is doubtful, whether the matter be carried out with such mathe- 

 matical precision. In any case, after the reduction is complete, we 

 are not dealing with half cells, for in the forerunners of both male 

 and female gametes there are usually two further divisions to form the 

 latter. As these two mitoses cannot possibly be qualitative — in the 

 absence of a "reducing division" — the egg and its three polar bodies 

 must be identical gametes in all essential characters (except size), 

 and the hke must be true of the four spermatozoa formed from one 

 spermatocyte. The amount of variation, of variety, assumed by 

 Weismann to obtain in the gametes, and to be induced by a re- 

 ducing division, is far greater than is required by the facts. Indeed, 

 it may be doubted, whether under it „offspring" could bear any great 

 resemblance to their immediate "ancestors" ^). 



1) Owing to the facts, concerning the course of the development 

 from one generation to the next, and to the mode of formation or 

 evolution of the embryo from one primary germ-cell, as revealed by 

 the writer's researches, the words "offspring" and "ancestor" possess no 



