TRANSMISSION OF ACQUIRED CHARACTERS. 389 



light of the theory of natural selection had fallen on these pheno- 

 mena; at that time we should have been far from right if we 

 had assumed that organisms possess a power which causes them 

 to respond to external influences by useful modifications, a power 

 unknown elsewhere, entirely unproved and only supported by the 

 fact that at that time it did not seem possible to explain the 

 phenomena in any other way. 



Although my theory has not been disproved, I will nevertheless 

 attempt to bring into further accordance with it certain phenomena 

 which seem at first sight to oppose it. I first began to take this 

 course in my paper ' On Heredity V In that paper I attempted to 

 show how the fact that disused organs become rudimentary may 

 be readily explained without assuming the transmission of acquired 

 characters ; and also that the origin of instincts may in all cases 

 be referred to the process of natural selection 2 , although many 

 observers had followed Darwin in explaining them as inherited 

 habits, a view which becomes untenable if the habits adopted 

 and practised in a single life cannot be transmitted. 



Other phenomena which appeared to present difficulties were 

 also considered and brought into accordance with the theory, and 

 I think that I have been successful in showing that adequate and 

 simple explanations may be given. 



There certainly remain many phenomena which seem to be 

 opposed to my theory and for which a new explanation must be 

 found. Thus Romanes 3 , following Herbert Spencer 4 , has recently 

 pointed to the phenomena of correlation as a proof of the trans- 

 mission of acquired characters ; but, at no distant time, I hope to 

 be able to consider this objection, and to show that the apparent 

 support given to the old idea is in reality insecure and breaks 

 down as soon as it is critically examined. I believe that I shall 

 be able to prove that correlation cannot be used as the indirect 

 proof of an hypothesis, of which all direct evidence is still com- 



1 See the second Essay. 



[ 2 See E. Meldola in Ann. and Mag. Nat. Hist., 1878, vol. i. pp. 158-161. The 

 author discusses many cases among insects in which instinct is related to protective 

 structure or colouring : he also considers that instinct is to be explained by the 

 principle of natural selection which accounts for the other protective features. 

 E. B. P.] 



[ 3 See ' Nature,' vol. 36, pp. 491-407. E. B. P.] 



[ 4 See ' The Factors of organic Evolution ' in ' The Nineteenth Century ' for April 

 and May 1886. E. B. P.] 



