56 THE FIRST PRINCIPLES OF HEREDITY 



Not only is this biologically inconceivable, but it has been 

 definitely disproved by Galton by experiments expressly 

 made for that purpose. To obviate this difficulty, there- 

 fore, Galton himself propounded a new theory of heredity in 

 1875, which, with its insistence on the distinction between 

 body-cells and germ-cells, may be taken as a type of all 

 successive theories of germinal continuity. 



Galton uses the word " stirp " (stirpes, Latin =root) " to 

 express the sum total of germs (gemmules), or whatever 

 they may be called, which are to be found in the newly- 

 fertilized ovum " (or in a budding-point of an organism). 

 " The stirp contains a host of germs, much greater in 

 number and variety than the organic units of the structure 

 that is about to be derived from them, so that compara- 

 tively few germs achieve development." Further, " the 

 germs that are not developed retain their vitality ; they 

 propagate themselves while still in a latent state, and they 

 contribute to form the stirp of the offspring." 



We have therefore, according to Galton, the stirp 

 divided into two parts, the " dominant " germs developing 

 into the body of the individual and the " residual " germs 

 which form the sex-cells of that individual, and, propagating 

 themselves, give rise to the next progeny. There is thus 

 direct descent between stirp and stirp, and not, as hitherto 

 assumed, between body and body. Indeed, Galton's 

 theory was devised mainly to account for the genetic 

 relationship between successive generations. Only as an 

 act of grace, as it were, did he assent to a very limited 

 possibility of the transmission of acquired characters. 

 For that purpose he admitted Darwin's explanation that, 

 exceptional^, a few germs may be thrown off by the body- 

 cells, which, finding their way into the germ-cells, are 

 incorporated with them. 



