(| xxvii) 
range of the system. The logical tendency of such a group 
would be to extend its limits indefinitely and not to give rise 
to repeated changes of the colour-type. 
Another difficulty was presented by the very close resem- 
blance, at times amounting to identity in external characters, 
between certain pairs in these groups, a resemblance to 
which Brunner’s epithet, ‘‘ hypertelic’’ might be applied. 
Existing theories postulated a selective elimination by insecti- 
vorous birds, etc. ; but the birds’ discrimination of members of 
a ‘ Millerian,” 7.¢., protected group must be in relation to 
its distinctness from the other insects co-existing in the same 
region. If, as was frequently the case, such a group was 
immediately recognisable by its broad features as protected 
and inedible, such further discrimination between its members 
as would be necessary to bring about the intimate likeness 
found, e.g., between many species of Melinwa and Heliconius 
was not adequately accounted for by Muller’s hypothesis. 
With regard to ‘ convergence,”’ which had been put forward 
as a necessary phenomenon in Millerian mimicry, the 
possibility of parallel variation ought not to be excluded. To 
take the case of H. thelxiope and H. vesta, the “ typical ”’ 
forms might be assumed, ew hypothes?, to be the most ancestral, 
and to have acquired their common resemblance by conver- 
gence; but from these forms were derived, as the series 
exhibited showed, a number of paired varieties which were 
progressively modified in relation to their distribution. There 
was nothing to show that either species had been influenced 
in its variation by the other, and that it would not have 
followed the same course if it had been isolated. And it was 
conceivable that the causes, in most cases unknown, which 
brought about modifications in the colour and markings of a 
species in association with its geographical range, might have 
produced identical results in two species of the same genus, 
with a common facies, under common conditions. 
Prof. Pounron: He congratulated Dr. Dixey on his care- 
ful work, and on the deep interest of the results he had 
obtained. It was a great source of satisfaction to him that 
this research had been conducted in the Hope Department of 
the Oxford University Museum. 
