WCP4887

[1]

Holly House,

Barking, E,

March 6^th. 1872

Dear Sir Charles

Darwin’s reply to Mivart¹ on the eye question does not seem to me satisfactory, as I have just told him. His statement that — "an organ for vision must be formed of transparent tissue" — is not correct. We know that all the invisible rays of the spectrum, including the heat rays, are conveyed by lenses & form invisible pictures so to speak. Eyes, therefore, might utilize the chemical or other rays invisible to us, and thus be formed of (to our eyes) opaque tissues. Considering that the invisible rays are more numerous in sunlight than those visible to us, it is marvellous that many[?] eyes² [2] developed three times independently (in Molluscs, Insects, & Vertebrates,) [yet] none should have used these rays, but all use just the same fraction of the spectrum that we use.

In order to give Darwin the full benefit of his reply you might add to the summary of Mivart’s argument a passage such as that put on the opposite page³. I think that will make the statement as fair to one as to the other. I have not seen Henson’s⁴ pamphlet & know nothing of the subject except in a general way.

Believe me | Yours very sincerely | Alfred R. Wallace [signature]

[3] "In the 6th. Edition of "Origin of Species" just published, Mr Darwin ^has replied to this objection by denying that the resemblance ^{in the case}[?] ^{of the eye formation} is more than general; and maintainsing that the necessary conditions of vision would inevitably lead to the amount of similarity which exists in eyes formed independently by the selection of favourable variations. " [4]⁵