- Correspondence with Charles Darwin 185 Galton next defines the word 'stirp' to
"express the sum total of the germs, gemmules or whatever they may be called, which are to be found, according to every theory of organic units, in the newly fertilised ovum-that is in the early pre-embryonic stage-from which time it receives nothing further from its parents, not even from its mother, than mere nutriment' This word `stirp,' which I shall venture to use, is equally applicable to the contents of buds, and will, I think, be found very convenient,
and cannot apparently lead to misapprehension."
We now pass to the essential features of Galton's theory, which corresponds far more closely than Darwin's to modern ideas, indeed it is often difficult to say how much modern ideas have taken from Galton-without acknowledgment of the source.
The stirp is the organised aggregate of organic units, or germs. The personal structure develops by selection out of a small portion of these units, and the sexual elements of the new individual are generated by the residuum of the stirp. There is no free circulation of gemmules from the cells to be aggregated in the sexual organs. When the somatic elements are being formed from the stirp any segmentation may contain `stray and alien gemmules,' and many of these may become entangled and find- lodgment in the tissue. When these gemmules are lodged in great variety, the somatic cells are really reproductive cells and thus Galton would account for the replacement of a lost limb in the lower animals, or the reparation of simple tissues in the higher ones. The selection of organic units to form the somatic characters of the individual from the whole host in his stirp Galton looks upon as of the highest importance. He considers that a sort of struggle for place goes on among the innumerable germs of the stirp, and those germs which are most frequent or have certain intrinsic qualities will be most successful. He considers that this continual selection leads ultimately in unisexual reproduction to the elimination of necessary units and so to degeneration; sex, he argues, is not primary, but a result of the advantage of a more primary double parentage, which lessens the chance of one or more of the needful species of germs in the stirp disappearing by selection'. Galton even goes so far as to suggest that where an excess of germs has been withdrawn from the stirp to form a marked character, for example, great ability or even a pathological state, there will be an absence of these germs in the residue, which goes to form the new sexual element, and he accordingly accounts in this way for the offspring of a man of genius having small ability, or again
' Galton (p. 341) very aptly remarks that if pangenetic gemmules circulated freely through the system, there can be little doubt that they would reach the body of an unborn child. Thus the paternal gemmules in that body would be dominated by an invasion of maternal gemmules with the final result that an individual would transmit maternal peculiarities far more than paternal ones; "in other words people would resemble their maternal grandmothers very much more than other grandparents, which is not at all the case."
' The "dominant germs" are "those that achieve development." (p. 341.)
3 "There is yet another advantage in double parentage, namely that as the stirp whence the child sprang is only half the size of the combined stirps of his two parents, it follows that one-half of his possible heritage must have been suppressed. This implies a sharp struggle for
place among the competing germs, and the success, as we may infer, of the otter half of their numerous varieties." (p. 334.)