1881 PANGENESIS AND PEEIGENESIS 93 



From G. J. Romanes to C. Darwin, Esq. 



By this post I return you Hackel's essay on 

 Perigenesis. Although I have kept it so long, I have 

 only just read it, as you said there was no need to 

 return it at any particular time. 



To me it seems that whatever merit Hackel's 

 ■^•iews may have in this matter, they certainly have 

 no claim to be regarded as origitial ; for I cannot see 

 that his ' Plastidules ' differ in anything but in name 

 from Spencer's ' Physiological Units.' Why he does 

 not acknowledge this, it is difi&cult to understand. 

 Anyhow, the theories being the same, the same 

 objections apply ; and to me it has alwaj^s seemed 

 that this theory is unsatisfactory because so general. 

 As you observe in your letter, everyone behoves in 

 molecular movements of some kind ; but to offer this 

 as a full explanation of heredity seems to me like 

 saying that the cause, say, of an obscure disease Hke 

 diabetes, is the persistence of force. No doubt this is 

 the ultimate cause, but the pathologist requires some 

 more proximate causes if his science is to be of any 

 value. Similarly, I do not see that biology gains 

 anything by a theory which is reaUy but little better 

 than a restatement of the mystery of heredity in 

 terms of the highest abstraction. Pangenesis at 

 least has the merit of supplpng us with some con- 

 ceivable carriers, so to speak, of the modified pro- 

 toplasm from the various organs or parts of the parent 

 to the corresponding organs or parts of the offspring, 

 and the multiphcation of gemmules seems to me to 

 avoid a difficulty with which Perigenesis (as stated by 



