96 VARIABILITY 



some less resistant germ-plasm. Granting that species have arisen 

 through Natural Selection, then the hereditary potentialities which 

 enable the germ-cells to develop into higher individuals (embryos 

 and adults) are of course due to selection occurring amongst the 

 latter ; but the characters that fit them to their own environments, 

 for example the locomotory tail of the spermatozoon, are equally of 

 course due to selection occurring amongst themselves. The selection 

 that maintains the stability of the germ-plasm, therefore, falls first 

 of all on the germs which cannot survive as cells if the germ-plasm 

 is much altered, or develop into higher organisms if it is more than 

 a little altered. Evolution is never perfect ; it is probable, therefore, 

 that many, perhaps very many, germs vary unfavourably in this 

 particular and perish, and that to this circumstance is due the fact 

 that evidence of germinal alteration resulting from the direct action 

 of the environment is rarely found amongst adult individuals. 



155. Germ-cells are very numerous amongst the higher animals, 

 though the number of possible offspring is small. Thus, the germ- 

 cells of such an organism as man exceed a million-fold the number 

 of his children. This superabundance, like all other characters of 

 the species, is, presumably, an adaptation. According to accepted 

 doctrine it serves to ensure fertilization. But nature is very 

 parsimonious of her materials, and when we remember the per- 

 fection of her adaptations (e.g. the eye, the ear, or the digestive 

 organs), the device of providing a vast multitude of cells in order 

 to secure the fertilization of a very few seems so unnecessarily 

 wasteful and clumsy as to awaken a suspicion of the correctness 

 of the interpretation. Such a device may be necessary when the 

 germ-cells are scattered broadcast in the environment and meet 

 by chance, as in the case of some plants, but hardly when they 

 enter a special receptacle in the body of the female. It seems not 

 improbable, therefore, that the function of the apparent super- 

 abundance is to provide materials for a selection which serves, 

 above all, to maintain the resisting power of the germ-plasm. At 

 any rate material in which such a selection can occur is provided 

 as abundantly by the higher animals as by the lower. 



156. Leaving aside the question as to how precisely the high 

 insusceptibility of the germ-plasm has been evolved, there can, 

 as I say, be no doubt of its existence. But though the germ-plasm 

 possesses high powers of resisting enforced change, though death 

 usually accompanies such change, it does not follow that con- 

 ditions cannot be found in which the germ-plasm is altered 

 and yet not destroyed. Thus, Clayton's beans progressively 



