NOTES AND MEMORANDA. 333 



developed in the generation which immediately succeeds, but 

 are often transmitted in a dormant state during many gener- 

 ations, and are then developed. Their development is sup- 

 posed to depend on their union with other partially developed 

 cells or gemmules which precede them in the regular course 

 of growth." 



He nowhere gives any opinion as to the actual size of 

 gemmules, or the number present in particular cases, but it 

 appears to me interesting to consider how far the theory will 

 hold good when examined from this more physical point of 

 view. 



For the sake of argument, I assume that gemmules on an 

 average contain one million structural molecules of albumen 

 and molecularly combined water. Variations in number, 

 composition, and arrangement would then admit of an almost 

 infinite variety of characters. On this supposition it would 

 require a thousand gemmules to be massed together into a 

 sphere, in order to form a speck just distinctly visible with 

 our highest and best magnifying powers. By calculation I 

 find that a single mammalian spermatozoon might contain so 

 many of such gemmules, that, if one were lost, destroyed, or 

 fully developed in each second, they would not be completely 

 exhausted until after the period of one month. Hence, since 

 probably a number are concerned in producing perfect fertili- 

 sation, we can readily understand why the influence of the 

 male parent may be very marked, even after having been, as 

 regards particular characters, apparently dormant for many 

 years. 



In a similar manner I calculate that the gprminal vesicle 

 of a mammalian ovum might contain enough gemmules for 

 one to be destroyed, lost, or fully developed in each second, 

 and yet the entire number not be exhausted until after a 

 period of seventeen years, and the entire ovum might contain 

 enough to last at the same rate for no less than 5,600 years. 



These calculations are made on the supposition that the 

 entire mass is composed of gemmules. Of this there is 

 little probability ; but still, even if a considerable portion of 

 the ovum consists of completely formed material and of mere 

 nutritive matter, it might yet contain a sufficient number of 

 gemmules to explain all the facts contemplated by the theory 

 of pangenesis. The presence of any considerable amount of 

 such passive matter in spermatozoa would, however, be a 

 serious difficulty in the way of the theory, unless indeed very 

 many spermatozoa are invariably concerned in producing 

 fertilisation. 



Taking everything into consideration, it does not appear 



