296 Professor E. B. Poulton on Mimetic Forms of 
would not remain intermediate, but would split up, in 
accordance with the Mendelian conception, into the parent 
forms; and we can thus understand the comparative 
rarity of intermediates. But while this is almost certainly 
true of the sub-species of dardanus in the W.,S.,and on the 
E. coast of Africa, where the specialization of the female 
forms has been carried to a high pitch, it is probably not 
equally true of the sub-species “nol ytrophus of the Kikuyu 
Escarpment. 
(«) Probable origin of planemoides from: carly variants 
of trimeni. 
The abundance of intermediates of all kinds among the 
females of polytrophus and the relative numbers of the 
ancestral form ¢7vimeni indicate a near approach to the 
origin of the diverse female forms. It is probable indeed 
that first-cross intermediates between the specialized forms 
themselves would split up into the parent forms on the 
Escarpment as in other parts of Africa; but it is by no 
means equally certain that the intermediates between each 
of them and their primitive ancestor trviment would behave 
in this manner. Only thus does it seem possible to ex- 
plain the relative abundance on the Escarpment of inter- 
mediates almost always exhibiting primitive characteristics, 
viz. Some approach to ¢riment. 
It would be of the highest interest to breed any of the 
sub-species of dardanus through several generations : 
especially is this desirable in “the case of “polytrophus, 
which is certain to yield results of the utmost importance 
from many points of view. 
It is probable that planemoides arose from triment by a 
combination of the varieties which were to produce cenea, 
hippocoon, and trophonius. ‘The size and shape of the white 
hind-wing patch probably arose from varieties on the way 
to cened, “its whiteness from those which were forming 
hippocoon, while the fulvous tint of the fore-wing was 
a utilization in another direction of the characteristic 
colouring of ¢rophonius. 
The argument made use of with regard to planemordes 
applies to all the other mimetic female forms; for inter- 
mediates between them occasionally occur probably in 
every sub-species and in all parts of the area of distribution. 
But while such varieties are not to be looked upon as 
ancestral, the case is very different with the Escarpment 
