Heredity and the Origin of Variations. 135 



the special centre of their accumulation. Hence it is the 

 paternal influence which makes for variation, the maternal 

 tendency being conservative. The reproductive cell is not 

 merely or chiefly a microcosm of gemmules. It is a cell 

 produced by ordinary cell-division from other reproductive 

 cells. The ovum remains comparatively unaffected by 

 changes in the body ; but it receives from the sperm, with 

 which it unites, gemmules from such tissues in the male 

 as were undergoing special modification. The hen does 

 not produce the egg ; but the cock does produce the sperm ; 

 and the union of the two hits the happy mean between the 

 conservatism of the one view and the progressive possi- 

 bilities of the other. 



Mr. Francis Galton, in 1876,* suggested a modification 

 of Darwin's hypothesis, which included, as does that of 

 Professor Brooks, the idea of germinal continuity which 

 had been suggested by Professor (now Sir Eichard) Owen, 

 in 1849. He calls the collection of gemmules in the 

 fertilized ovum the " stirp." Of the gemmules which con- 

 stitute the stirp only a certain number, and they the most 

 dominant, develop into the body-cells of the embryo. The 

 rest are retained unaltered to form the germinal cells and 

 keep up a continuous tradition. Mr. Galton's place in the 

 history of theories of heredity can scarcely be placed too 

 high. Only one further modification of pangenesis can 

 here be mentioned, namely, that proposed in 1883 by 

 Professor Herdman, of Liverpool. He suggested " that the 

 body of the individual is formed, not by the development 

 of gemmules alone and independently into cells, but by the 

 gemmules in the cells causing, by their affinities and 

 repulsions, these cells so to divide as to give rise to new 

 cells, tissues, and organs." 



Such are Darwin's provisional hypothesis of pangenesis, 

 and some more recent modifications thereof. Bold and 

 ingenious as was Darwin's speculation, supported as it at 



* For an excellent account of the genesis and growth of the modern views 

 of heredity, see Mr. J. Arthur Thomson's paper on " The History aud Theory 

 of Heredity : " Proceedings of the Royal Society of Edinburgh, 1S89. 



