WCP4527

[1]

Parkstone, Dorset.

June 10^th. 1893

My dear Meldola

As we had no time to "discourse" on Thursday, I will say a few words on the individual adaptability question. We have to deal with facts, & facts certainly show that, in many groups, there is a great amount of adaptable change produced in the individual by external conditions, & that that change is not inherited. I do not see that this places nat[ural] select[ion] in any subordinate position, because this individual adaptability is evidently [2] advantageous to many species & may itself have been produced or increased by nat[ural] select[ion]. When a species is subject to great changes of conditions, either locally or at uncertain times, it may be a decided advantage to it to become externally ^individually adapted to that change while retaining the power to revert ^instantly to its original condition ^form when the normal form conditions return. But whenever the changed conditions are permanent or are such that individual adaptation cannot meet the requirements, then [word crossed out] nat[ural] select[ion] rapidly brings about a permanent adaptation which [3] is inherited. In plants these two forms of adaptation are well marked & easily tested, and we shall soon have a large body of evidence upon it. In the higher animals I imagine that individual adaptation is small in amount, as indicated by the fact that even slight varieties often breed true.

In Lepidoptera we have the two forms of ^colour-adaptabilyity clearly shown. Many species are, in all their stages, permanently adapted to their environment. Others have a certain power of individual adaptation — as of the pupae to their surroundings. If this last adaptation [4]¹ were strictly inherited it would be positively injurious, since the progeny would therefore lose the power of individual adaptability, & thus we should have light pupae on dark surroundings & vice versâ. Each kind of adaptation has its own sphere, & it is essential that the one should be non-heritable the other heritable. The whole thing seems to me quite harmonious and "as it should be".

Thistelton Dyer²[sic] tells me that H[erbert] Spencer is dreadfully disturbed on the question. He fears that acquired characters may not be inherited, in which case the foundation of his whole philosophy is undermined!

Yours very truly| Alfred R. Wallace [signature]

P.S. I am afraid you are partly responsible for that kindly meant but too personal manifestation which disturbed the solemnity of the R[oyal] S[ociety] meeting on Thursday!!³

^{We hope to go to the Lakes & Derbyshire the week after this.4}