XXXIV MEMOIR. 
‘‘T have sent a copy to Mr. Darwin and to Mr. P. L. Sclater. Hoping 
that you may find time to read my paper and give me your opinion 
thereupon, 
‘« Believe me yours, 
“HH. W. BARES 
In his reply to this letter Dr. Hooker wrote encouragingly, as 
follows :— 
‘‘T thank you very much for the papers on the Amazonian Insect Fauna, 
which you have been good enough to send me. They seem to my judgment 
to be extremely well done, and they are most interesting and suggestive. I 
do not see how any accurate conclusions as to the migrations of species can 
be worked out without following the method you have pursued, and I suppose, 
as far as insects at least are concerned, have originated. Those you have 
arrived at appear to be logically and scientifically secure, and as such are 
great gains. I quite agree with all you say about the necessity of dis- 
tinguishing varieties as well as species. . . . I began science myself with 
entomology, but could not keep it up with botany, so as to do any good to 
either; but I was much struck in my small experience with the ample facility 
there was for working out questions of variation, owing to the readiness with 
which you can compare many specimens at one coup d@’ zl, and sort them in 
various diverging series. With plants this is almost impossible, except by 
covering the floor, or very large tables, which is the way I adopt.’’ 
Mr. Wallace’s letter is of interest as dealing with the Guiana 
region as a centre of distribution :— ) 
Myr. A. R. Wallace to H. W. Bates. 
‘* LOBO RAMAN, 100 MILES E. OF BENCOOLEN, 
‘« December toth, 1861. 
‘““MyY DEAR BATES, 
‘‘T should have written to you before to thank you for your paper on 
the ‘PaZgzizos,’ but 1 somehow never can post up my correspondence till I get 
into some savage wilderness like that in which I am at present. I have read 
your paper with great attention, and also with great pleasure, and I trust it 
is but the first of a long series which will establish your own fame, and at 
the same time demonstrate the simplicity and beauty of the Darwinian 
philosophy. 
‘Your paper is in every respect an admirable one, and incontestably 
proves the necessity of minute and exact observation over a wide extent of 
country to enable a man to grapple with the more difficult groups, unravel 
their synomy, and mark out the limits of the several species and varieties. 
All this you have done, and have besides established a very interesting fact 
in zoological geography,—that of the southern bank of the river having 
received its fauna from Guyana, and not from Brazil. There is, however, 
another fact I think of equal interest and importance, which you have barely 
