236 Evolution and Adaptation 



the gemmules that have collected in it. The fifth assumption 

 is that the gemmules are thrown off at all stages of develop- 

 ment ; the sixth, that in their dormant state they have a 

 mutual affinity for each other ; the seventh, that there may be 

 a sort of continual competition in the germ-cells between the 

 original gemmules and the new ones, and, according to which 

 win, the old or the new form develops. Thus we see on 

 closer analysis that the pangenesis hypothesis is made up of 

 a goodly number of different assumptions. At least half a 

 dozen imaginary properties are ascribed to the imaginary 

 gemmules, and these attributes are all essential to the 

 working of the hypothesis. 



Some of the more obvious objections to the hypothesis 

 have been stated by Darwin himself. Such, for instance, as 

 our ignorance at what stage in their history the body-cells are 

 capable of throwing off gemmules, and whether they collect 

 only at certain times in the reproductive organs, as the 

 increased flow of blood to these organs at certain seasons 

 might seem to indicate. Nor have we any evidence that they 

 are carried by the blood at all. The experiment of Galton, of 

 transfusing the blood of one animal into another, and finding 

 that this produced no effect on the young that were born 

 later, might be interpreted to mean that gemmules are not trans- 

 ported by the blood ; but this kind of experiment is inconclu- 

 sive, especially in the light of recent results on the effect of 

 the blood of one animal on that of another. 



A part of the evidence on which Darwin relied to support 

 his theory has been shown to be incorrect by later work. 

 Thus the assumption that more than a single pollen grain, or 

 more than one spermatozoon, is necessary in some cases for 

 fertilization, is certainly wrong. In most cases, in fact, the 

 entrance of more than one spermatozoon into the egg is dis- 

 astrous to the development. The cases referred to by Dar- 

 win can probably be explained by the difficulty that some of 

 the pollen grains, or spermatozoa, may have in penetrating 



