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.

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.