396 PROVISIONAL HYPOTUKSLS CiiAr. XXVII. 



do not readily blend, — blue plumage in the one case, evidently- 

 derived from the rock-pigeon, and red plumage in the other 

 case, derived from the wild jungle-cock, occasionally reappear. 

 With uncrossed breeds the same result follows, under condi- 

 tions which favour the multiplication and development of 

 certain dormant gemmules, as when animals become feral 

 and revert to their pristine character. A certain number of 

 gemmules being requisite for the development of each cha- 

 racter, as is known to be the case from several spermatozoa 

 or pollen-grains being necessary for fertilisation, and time 

 favouring their multiplication, will perhaps account for the 

 curious cases, insisted on by Mr. Sedgwick, of certain diseases 

 which regularly appear in alternate generations. This like- 

 wise holds good, more or less strictly, with other weakly 

 inherited modifications. Hence, as I have heard it remarked, 

 certain diseases appear to gain strength by the intermission 

 of a generation. The transmission of dormant gemmules 

 during many successive generations is hardly in itself more 

 improbable, as previously remarked, than the retention 

 during many ages of rudimentary organs, or even only of a 

 tendency to the production of a rudiment ; but there is no 

 reason to suppose that dormant gemmules can be transmitted 

 and propagated for ever. Excessively minute and numerous 

 as they are believed to be, an infinite number derived, during 

 a long course of modification and descent, from each unit of 

 each progenitor, could not be supported or nourished by the 

 organism. But it does not seem improbable that certain 

 gemmules, under favourable conditions, should be retained 

 and go on multiplying for a much longer period than 

 others. Finally, on the view here given, we certainly gain 

 some insight into the wonderful fact that the child may 

 depart from the type of both its parents, and resemble its 

 grandparents, or ancestors removed by many hundreds of 

 generations. 



Conclusion. 



The hypothesis of Pangenesis, as applied to the several 

 great classes of facts just discussed, no doubt is extremely 

 complex, but so are the facts. The chief assumption is thafc 



