Thanks for sending paper on geological development (Dana 1856). Discusses infertility of species. Discusses first part of Asa Gray’s paper (A. Gray 1856–7). Thanks for note on the Cave Rat. Discusses a new species of fossil cirripede, in the genus Chthamalus. Explains his interest in pigeon breeding.
Asks TD about variation among brachiopods.
W. J. Hooker thinks Harvey will be willing to give information on reproduction of higher marine plants.
On the variety of species definitions prevalent among naturalists.
Notes on the comparative rarity of intermediate forms between species, and the varying relationships those forms may have to one or both species between which they are intermediate.
His experience confirms CD’s view that some species and even some genera of Brachiopoda are consistently more variable than others, and that such variable forms are variable in all localities and at all periods. Similarly a species that shows a lack of variability does so at all points in time and space. Discusses the causes of variability. [See Natural selection, p. 106.]
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