262 PSEUDACRAEA EURYTUS 



natural, and to be expected after such exciting intelli- 

 gence." 



Again, on October 26, 1912, Professor Poulton wrote : 

 ** I am glad that you are realizing the great importance 

 of this material as a test for Natural Selection against 

 Mutation. It seems almost too good to be true. ..." 

 On November 22, 1912, he again wrote : 

 "I do not doubt that imitator in Natal is just as 

 successful as eurytus on the West Coast. Probably 

 nowhere in Africa are Pseudacraeas quite as successful 

 as they are in Uganda. But on the West Coast they 

 are very polymorphic, in Natal monomorphic, yet both 

 about equally successful. I take it that any variety in 

 Natal that might lead on to a new form is at once exter- 

 minated because there is only one Planema there, namely 

 aganice, but on the West Coast there are many models, 

 and any variety leading to one of them causes the varia- 

 tion to fall into the surviving percentage. If that model 

 disappeared the form would then drop out. We get all 

 this happening round Entebbe according as the models 

 change or disappear " (e.g. the change in hohleyi from white 

 banded to brown banded hind wing, and of the female 

 from tirikensis to poggeoides in different proportions in 

 different parts of Uganda). " Only to-day I saw the male 

 hohleyi from Neave's Western Uganda series with a brown 

 bar crossing the hind wing, and in the same lot was the 

 Planema, a form of macarista with a similar male." (This 

 form is known as pseudeuryta, and has been already 

 alluded to.) 



"I do not believe that any of these mimics depend 

 for their existence on the model. The pattern depends 

 for its existence on the model, but not the species which 

 produces the j)attern. That is to say, Pseudacraea 

 eurytus is a species which could stand by itself, and indeed 

 does so on certain islands where the protection afforded 

 by Planema models is non-existent, but the form 



