S68 THE STUDY OF ANIMAL LIFE CHAP. 



conclusion that " the doctrine of pangenesis, pure and 

 simple, is incorrect." His own view was that the 

 fertilised ovum consisted of a sum of germs, gemmules, 

 or organic units of some kind, to which in entirety he 

 applied the term stirp. But he did not regard this nest 

 of organic units as composed of contributions from all 

 parts of the body. He regarded it as directly derived from 

 a previous nest, namely, from the ovum w r hich gave rise 

 to the parent. He maintained that in development the 

 bulk of the stirp grew into the body as every one allows 

 -but that a certain residue was kept apart from the 

 development of the " body ' to form the reproductive 

 elements of the offspring. Thus, he said, in a sense the 

 child is as old as the parent, for when the parent is develop- 

 ing from the ovum a residue of that ovum is kept apart 

 to form the germ-cells, one of which may become a 

 child. Besides Galton, Jaeger, and Brooks, several other 

 biologists suggested this fertile idea of the organic con- 

 tinuity of generations. It was recognised by Erasmus 

 Darwin and by Owen, by Haeckel, Rauber, and Nussbaum. 

 But it is to Weismann that the modern emphasis on 

 the idea is chiefly due. 



Let us try to realise this doctrine of organic continuity 

 between generations. Let us begin with a fertilised 

 egg-cell, and suppose it to have the potential qualities 

 abcxyz. This endowed egg-cell divides and redivides, and 

 for a short time each of the units in the ball of cells may be 

 regarded as still possessing in equal measure the qualities 

 abcxyz. But division of labour, and rearrangement, in- 

 folding and outfolding, soon begin, and most of the cells 

 f}rm the "body." They lose their primitive characters 

 and uniformity, they become differentiated, the qualities 

 ab find predominant expression in one set, be in another, 

 xy in another, and so on. It may be that all the qualities 

 are possessed by all the cells, and that only two or three 

 find expression while the others lie quite latent, like 

 dormant seeds, unless some unusual stimulus calls them 

 into expression. But while the body-making and the 

 associated differentiation have been going on, certain 

 cells have taken no share in it. They have remained 



