(26) 
was at systematic work I know I longed to have no other 
difficulty (great enough) than deciding whether the form was 
distinct enough to deserve a name, and not to be haunted with 
undefined and unanswerable questions whether it was a true 
species. What a jump it is from a well-marked variety, pro- 
duced by natural cause, to a species produced by the separate 
act of the hand of God! But I am running on foolishly. 
By the way, I met the other day Phillips, the paleontologist, 
and he asked me, ‘ How do you define a species?’ I answered, 
‘IT cannot.’ Whereupon he said, ‘ At last I have found out 
the only. true definition—any form which has ever had a 
specific name !’”’ * 
The idea of a species as an inter-breeding community, as 
syngamic, is, I believe, the more or less acknowledged found- 
ation of the importance given to transition. This will become 
clearer from the consideration of a concrete example. The 
common black-and-white Danaine butterfly, Amauris niavius 
of West Africa, is represented on the East and South-East 
Coasts by a very similar butterfly, distinguished by the greater 
size of the largest white patch, and of the white spot in the 
cell of the fore-wing. Both forms are very constant in the 
areas over which they were known, and on these constant 
easily recognisable characters the eastern butterfly was 
described as a distinct species under the name of A. domint- 
canus. Aurivillius, however, in his valuable Catalogue refuses 
to recognise this latter as a distinct species, and considers it 
as the dominicanus variety of niavius. Through the kind- 
ness of Mr. C. A. Wiggins and Mr. A. H. Harrison, the Hope 
Department has recently been presented with an exceedingly 
fine series of butterflies from both east and west of the 
northern shores of Lake Victoria Nyanza. These have been 
carefully studied by Mr. 8S. A. Neave, B.A., of Magdalen 
College, Oxford, who finds that the typical niavivs occurs in 
great abundance to the west of the lake, while on the east he 
meets, in both collections, with varieties beautifully inter- 
mediate between it and dominicanus. These varieties, 
occurring precisely in the zone where the eastern form meets 
the western, complete for the systematist the transition which 
* “* More Letters,” vol. i, p. 127, Letter 79. 
