106 Dr. Arthur G. Butler on 
satisfied that in an unusually dry country the so-called 
“wet-season form” is sometimes identical with the so- 
called ‘‘ dry-season form” of a moister country. Indeed, 
the conditions, as far as the absence of one modification 
and presence of a new one are concerned, are practically 
very similar to those which obtain in the N. American 
Lyceenid, Cyaniris pseudargiolus, beautifully worked 
out by Mr. W. H. Edwards (Butt., N. Am., u., pp. 315 
et seq.). 
Mr. Marshall is quite correct in saying that it is 
extremely difficult to define ‘‘the specific differences of 
butterfles merely from a series of museum specimens 
when not backed up by a practical knowledge of 
the habits and range of the species involved.” But, 
on the other hand, it is impossible for a worker in any 
one part of so vast a country as Africa arbitrarily to 
settle, to the satisfaction of everyone, the extent of varia- 
tion of any one widely distributed species under seasonal 
and climatic conditions. That Mr. Marshall has amply 
proved this I can readily show; and 1 do so, not with 
any desire to detract from the value of his observations, 
as applied to South African butterflies when in southern 
S. Africa, but to prove that the conditions differ in 
the same species when found only so far northward as 
Nyasaland. 
' In my notes on “Seasonal Dimorphism in Acraa” I 
took what I regarded as the extreme dry and wet 
developments of the species, not of that phase of the 
species represented either in the Cape Colony or in 
Mashunaland ; whether the intermediate forms occur as 
the dry-season form in one part of Africa, the wet-season 
form in another, as the sole representatives of the species 
in a third, or not at all ina fourth, is perfectly immaterial. 
As developments of the species, intimately connected 
with and incapable of separation from it, they must be 
taken into account; but I frankly admit that it is 
extremely probable, as already granted, that I ought to 
have called the dry-season form ‘ wet,” and the wet form 
“dry.” The fact, therefore, that one of my seasonal 
forms does not occur in conjunction with the extreme 
southern form throughout its range, or that it occurs 
apart from the latter at any part of its range, 13 not 
enough to show that it is not a seasonal phase of a species 
in some part of Africa. 
