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The Dell, Grays, Essex.  November 15, 1872.

Dear Darwin,—­I should have written earlier to thank you for your book,[94] but was hoping to be able to read more of it before doing so.  I have not, however, found time to get beyond the first three chapters, but that is quite sufficient to show me how exceedingly interesting you have made the subject, and how completely and admirably you have worked it out.  I expect it will be one of the most popular of your works.  I have just been asked to write a review of it for the Quarterly Journal of Science, for which purpose I shall be in duty bound to seek out some deficiencies, however minute, so as to give my notice some flavour of criticism.

The cuts and photos are admirable, and my little boy and girl seized it at once to look at the naughty babies.

With best wishes, believe me yours very faithfully,

ALFRED R. WALLACE.

P.S.—­I will take this opportunity of asking you if you know of any book that will give me a complete catalogue of vertebrate fossils with some indication of their affinities.—­A.R.W.

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Down, Beckenham, Kent.  January 13, 1873.

My dear Wallace,—­I have read your review with much interest, and I thank you sincerely for the very kind spirit in which it is written.  I cannot say that I am convinced by your criticisms.[95] If you have ever actually observed a kitten sucking and pounding with extended toes its mother, and then seen the same kitten when a little older doing the same thing on a soft shawl, and ultimately an old cat (as I have seen), and do not admit that it is identically the same action, I am astonished.

With respect to the decapitated frog,[96] I have always heard of Pflueger as a most trustworthy observer.  If, indeed, anyone knows a frog’s habits so well as to say that it never rubs off a bit of leaf or other object, which may stick to its thigh, in the same manner as it did the acid, your objection would be valid.  Some of Flourens’ experiments, in which he removed the cerebral hemisphere from a pigeon, indicate that acts apparently performed consciously can be done without consciousness—­I presume through the force of habit; in which case it would appear that intellectual power is not brought into play.  Several persons have made such suggestions and objections as yours about the hands being held up in astonishment:[97] if there was any straining of the muscles, as with protruded arms under fright, I would agree:  as it is I must keep to my old opinion, and I daresay you will say that I am an obstinate old blockhead.—­My dear Wallace, yours very sincerely,

CH.  DARWIN.

The book has sold wonderfully; 9,000 copies have now been printed.

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The Dell, Grays, Essex.  Wednesday morning, [November, 1873].