G xxvii") 
original habitat in Tropical America.* But whereas certain 
groups, such as 1, 2, 3, and 4, were of extensive geographical 
range, others, such as the Ega group, 5a, with its peculiar 
suffused brown coloration, or the Rio Napo group, 5c, were 
restricted to a comparatively small area. This was intelligible 
in the Andean region, where every valley had its owu special set 
of forms and where isolation played the same part as in the 
evolution of insular faunas, but, as Dates had pointed out, 
it was a very remarkable phenomenon in the Amazon valley, 
throughout which the physical conditions were very uniform. 
He did not propose to dispute either of the theories of mimi- 
ery which were associated with the names of Bates and 
Miller, but they rested very largely on hypothesis and were 
in want of further support from observation and experi- 
ment, which would afford a large if arduous field of 
work to the enterprising naturalist; the difficulties of the 
subject did not appear to him to be fully overcome by these 
theories, which should not be pushed so far as to lead to the 
disregard of other factors which might have influenced the 
genesis of these groups. One difficulty was that of distribu- 
tion. As before mentioned, the groups of the Upper Amazon 
valley were often of limited range; but if they were geneti- 
cally connected and the conditions of their environment were 
constant, the causes which brought about association under 
a common type, if prohibiting deviation therefrom under 
penalty of destruction, should have operated to extend the 
limits of a group as widely as possible by acting as a check 
to variation on its outskirts. If it were assumed that one 
form were so far dominant as to drag its associates with it in 
any given direction, it must be also recollected that the prin- 
ciple on which these large ‘ Miullerian”’ associations were 
supposed to be based was prohibitive to variation of any 
component species, either as a whole, or in any part of the 
* As an example, group 4 is distinguished mainly by having 
the hindwings almost or quite black behind the transverse black 
bar usually preseut. The same character exists in British Guiana 
examples of //. theluiope and //. vestu, not in other respects true 
components of the group; it is absent in their Amazon repre- 
sentatives, at least as far as Bolivia, where it turns up again in 
association with very different groups. 
