I quite agree that it must have been small; yet the more I go into that question the more convinced I feel that there was during the Glacial period some migration from north to south.
The sketch in the "Origin" gives a very meagre account of my fuller MS.
essay on this subject.
I shall be particularly obliged for a copy of your paper when published (118/2.

Probably a paper by Bates entitled "Contributions to an Insect Fauna of the Amazon Valley" ("Trans.

Entomol.

Soc." Volume V., page 335, 1858-61).); and if any suggestions occur to me (not that you require any) or questions, I will write and ask.
I have at once to prepare a new edition of the "Origin," (118/3.

Third Edition, March, 1861.), and I will do myself the pleasure of sending you a copy; but it will be only very slightly altered.
Cases of neuter ants, divided into castes, with intermediate gradations (which I imagine are rare) interest me much.