Extended discussion of their respective difficulties with the definition and status of species and with the extent to which the theory of transmutation may be applied.

Has rediscovered S. S. Haldeman’s 1844 paper defending the transmutation theory with great skill.

Asks for reference to Geoffroy Saint-Hilaire’s first enunciation of the progressive development and transmutation theory.

Discusses S. S. Haldeman’s paper ["Enumeration of the recent freshwater Mollusca", Boston J. Nat. Hist. 4 (1844): 468–84].

Centres of species origin.

Describes his corrections of Origin.

Thanks CL for copy of his paper ["Structure of lavas", Philos. Trans. R. Soc. Lond. 148 (1858): 703–86].

Promises him a copy of Origin.