From G. R. Crotch 19 [February 1871]1
Allow me to thank you for your book—2 what a blessing to have the edges cut— you will take off 5/c of unpopularity by that—a new form of selection—3 I have just read Mivartts book—4 he degenerates so rapidly after the middle as to be quite curious, some points are well urged—but reiteration is tedious especially of cuts. There is a tendency to justify Pangenesis up here & to bring mathematical illustrations of it which seem good—5 Wallace’s address on Madeira will not convince me at any rate— he misapprehends the point besides making gross mistakes—(e.g. apterous Rhizotrogus)—my idea being that the islands if connected were of course then summits of mountains—6 now the apterous genera he does not find there are almost all denizens of the low sandy flats by the sea & rivers of Spain & Morocco—which would not be able to go upward as the land sank & hence were destroyed— the few apterous genera in common, Tarphius—Acalles—etc are precisely found in the Pyreneees the Apennines etc—& are mountain things—7 that Colonization has played a large part I don’t doubt, but there is evidence I think of connection—
in pressing the Tarphius question he forgets the Indian Tarphii from the Himalayas also— The absence of certain groups as Carabus, Rhizotrogus etc is the less unaccountable—as they all occur in Canary—which is otherwise so similar— There also the low sandy islets which remain are provided with precisely all those genera of Pimelia Brachycerus etc.8 The azores are better for him but I consider they have hardly been collected—& certainly that nearly all their fauna is gone from them now.9
Yr GR Crotch
Thanks for presentation copy of Descent.
Mivart’s Genesis of species  is poor.
Mathematical illustrations of Pangenesis at Cambridge.
Wallace’s address on Madeira not convincing ["The President’s Address", Trans. R. Entomol. Soc. Lond. (1870): xliv–lxix; A. R. Wallace, Studies scientific and social (1900) 1: 250–66].
Please cite as
Darwin Correspondence Project, “Letter no. 7491,” accessed on 9 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-7491