Has enjoyed reading LA’s book [Études sur les glaciers (1840)].

Hopes LA will pardon manner in which CD has alluded to his work on glaciers in his Journal of researches, of which he sends a copy.

Thanks LA and sends thanks to A. A. Gould for specimens. Describes principal findings of his research on cirripedes. Is obliged for information Joseph Leidy gave about cirripede eyes. Describes anatomical features and chief aspects of growth. Describes discovery of parasitic males and a species parasitic upon other cirripedes.

Thanks LA for presentation copy of his book, Lake Superior [1850].

Comments on species of cirripedes sent by LA and A. A. Gould.

Thanks LA for presentation copy of Contributions [to the natural history of the United States of America, vol. 1, pt 1: Essay on classification, and vol. 1, pt 2: North American Testudinata (1857)]. Flattered; CD sees there is much of highest interest to him.

Sends copy of Origin.

Introduces J. P. Lesley, "the most accomplished geologist of the United States".

Thanks LA for Methods of study [1863].

Is gratified that he has not taken a personal dislike to CD, though he is strongly opposed to nearly everything CD has written.

LA clarifies his opposition to CD’s views, which does not blind him to the great value of CD’s original researches.

Answers CD’s questions regarding sexual coloration of Amazonian fishes and the protuberances on the head of male Geophagus and Cichla during the spawning season [see Descent, pp. 520, 529].

Thanks LA for information on sexual differences in the coloration of Amazonian fish. CD was anxious to know how the sexes differed because they are unusual in that the male has the largest share in looking after ova and young.

Introduces his son Alexander; believes CD will find him "more tractable" on certain questions than LA himself is.