acted as a model for the other. The pattern which they bear 
in common is characteristic of the females of a group of western 
Planemas, and we may here be witnessing an example of arrested 
divergence among the descendants of a common ancestor, which 
arose under the influence of the black and white Danaines. The 
possible incipient mimicry of the models of Combination I by the 
male of Pl. alcinoe has been spoken ofon page 493. 
The mimetic females of Acrwa jodutta Y. 
Three different female forms of this species — all mimetic — 
were captured at Entebbe during the period under consideration 
in the present memoir : 47 white-marked mimics (the carmentis- 
form) of the females of Planema macari ta and Pl. alcinoe (Combin- 
ation II), 23 fulvous-marked mimics of Planema tellus platyxantha 
(Combination III), and 4 fulvous-and-white-marked mimics of Dan- 
aida chrysippus L. These latter combine the Zellus-like pattern 
with the white subapical bar of carmentis. Their comparative rarity 
is probably due to the fact that D. chrysippus is not nearly so 
common as the Planemas in the forests where these collections 
were made and where A. jodutta abounds. 
Assuming, from its close resemblance to the pattern of the non- 
mimetic male, that the white-marked carmentis is the older of the 
two principal female forms, it is a tempting hypothesis to suppose 
that the Zellus-like female has been produced from it by a sudden 
colour « mutation », in which the white has been replaced by 
fulvous. But the patterns are by no means identical, and the 
differences are such as to increase the likeness to their respective 
models. The fulvous area covers far more of the hind wing 
(extending further towards the base as well as towards the margin) 
of one form than the white does of the other, while the area due to 
the invasion of the fore wing by the fulvous of the hind is also 
larger, and of a different shape from that produced in the other 
form by the invasion of the white. It is unreasonable to suppose 
that these features, nicely adjusted as they are to the pattern of 
a species in another genus, sprang into existence, ready-made 
and complete, and at the same time as the change in colour. 
[have recently been given the opportunity of comparing,on a fair- 
ly complete scale, the pattern of the white-marked carmentis-form 
