236 Annals Entomological Society of America [Vol. II, 



bable hypothesis is that sharpsighted enemies, without analysing 

 the markings, recognize differences in degrees of likeness, and 

 that the selective pressure exercised by them is influenced by 

 the recognition. 



A great deal of attention is rightly directed at the present 

 day to the value of experiment, and indeed it is impossible to 

 over-estimate its importance. But while human performance is 

 of the deepest interest for the solution of mysteries innumerable, 

 of more profound significance still, for the comprehension of the 

 method of evolution, is the vast performance of Nature herself. ^-^ 

 Because of the bright promise it holds for the understanding of 

 Nature's experiments, I have brought before you the subject of 

 Mimicry in North American Butterflies. 



In the introductory words I spoke of the relationship of my 

 subject to the teachings of Darwin, and now I am anxious to con- 

 nect this address by a closer link to the personality of the illus- 

 trious naturalist. With the kind consent of Mr. Francis Darwin, 

 I am able to achieve this object by printing, for the first time, a 

 letter, recently discovered in the archives of the Hope Depart- 

 ment of Oxford, written by Darwin to the Founder in 1837. It 

 is concerned with the insect material collected on the Beagle 

 and is of peculiar interest because so few of Darwin's letters of 

 this early date have been preserved. The letter clearly exhibits 

 the keen interest which Darwin took in the working out of his 

 collections, and the free and generous use he made of his material. 

 A number of Diptera captured by him in Australia and Tasmania 

 — evidently gifts to Mr. Hope — exist in the Hope Department, 

 and are still in excellent condition. It is probable that species 

 of other groups collected by him are also present. 



Dear Hope 



I called yesterday on you and left a tin box with a few Hobart 

 Town beetles, which I had neglected to put with the others. Is not 

 there not [sic] a Chrysomela among them, very like the English species 

 which feeds on the Broom. — I have spoken to Waterhouse about the 

 Australian insects; you can have them when yoi: like. — The collections 

 in the pill boxes come from Sydney, Hobart town, and King George's 

 Sound. — Do you want all orders for your work? Some are already I 

 believe in the hands of Mr. Walker, and you know Waterhouse has 

 described some minute Coleoptera in the papers read to the Entomo- 



'^ See Carl H. Eigenmann in Fifty Y'ears of Darwinism, New York (1909), 

 208. 



