DARWIN'S HYPOTHESIS 407 



and consequently of material bulk, make a material theory 

 difficult. Modified force-centres, becoming further modified in 

 each generation, such as Mr. Spencer's physiological units, 

 might be made to fit in with Mr. Darwin's hypothesis in other 

 respects " (Ray Lankester, 1870, p. 32). " In fact, in place of 

 the theory of emission from the constituent cells of an organism 

 of material gemmules which circulate through the system and 

 affect every living cell, and accumulate in sperm-cells and 

 germ-cells, we may substitute the theory of transmission of 

 force, the two theories standing to one another in the same 

 relation as the emission and undulatory theories of light." 



But we fear that this suggestion has only prophetic value, for 

 we are not yet in biology in a position to utilise ideas of " modified 

 force-centres " or " transmission of force." We must creep 

 along with the slippery clue " metabolism " in our fingers ! 



One impression, however, we must emphasise — namely, that, 

 for the time Darwin's "provisional hypothesis of pangenesis " 

 had all the merits of a warrantable scientific hypothesis, and 

 had the marks of that insight of genius which the illustrious 

 author was wont' to deny in his humble conviction that " it's 

 dogged as does it." 



" Mr. Darwin wished to picture to himself, and to enable others 

 to picture to themselves, a process which would account for 

 (that is, hold together and explain) not merely the simpler facts 

 of hereditary transmission, but those very curious though abun- 

 dant cases in which a character is transmitted in a latent form, 

 and at last reappears after many generations, such cases being 

 known as ' atavism,' or ' reversion ' ; and again, those cases of 

 latent transmission in which characteristics special to the male 

 are transmitted to the male offspring through the female parent 

 without being manifest in her ; and yet again, the appearance 

 at a particular period of life of characters inherited and 

 remaining latent in the young organism." * 



* E. Ray Lankester, 1890, p. 279 ; Nature, July 15th, 1876. 



