OS 
While these theories cannot account for the great discrepaney in 
the systematics of the « models » and « mimics » except by falling 
back on accident, there is here no difficulty at all for the theory of 
natural selection. The theory offers a very simple explanation by 
assuming that the variable ancestor of the mimicking species has 
been gradually modified into a di- or polymorphic species by the 
weeding out of those intermediate forms which did not resemble 
protected species already existing in the country. The frequent 
rarity of intermediates is direct evidence for this theory. 
However, if we look closer at this explanation, we observe that 
the theory of natural selection does not exclude the forces of evo- 
lution on which the other theories solely depend. The ancester of 
the mimicking species varied in certain directions, which depended 
on the constitution of the species. One or the other individual 
variety was accidentally somewhat similar to a protected species. 
The range of distribution of the incipient mimic may have been 
extended, and its range of variation become larger under the 
influence of the new environment or the individual varieties become 
intensified, so that natural selection had a better field on which 
to operate. If one looks at evolution from this point of view, the 
antagonism between rival theories loses much of its acuteness. 
The systematics of the Butterflies in question teach us yet more. 
The figures of the di- and trimorphic species placed alongside the 
similar figures of distinct species seem to invite directly a certain 
line of thought. The figures appear to say this to us. The forms 
mima and wahlbergi of Hypolimnas (pl. XXIII, fig. 340, 334) — to 
restrict our remarks to one Insect for the sake of brevity — are still 
one and the same species, but if evolution proceeds further, they 
will attain to the same degree of diversity as the two Amauris 
which they resemble already in coloration (pl. XXIII, fig. 34, 35), 
i. e. the FORM mima will become SPECIES mima,and the FORM 
wahlbergi SPECIES wahlbergi. The occurrence of intermediate 
specimens in West Africa (and Madagascar as well) between the 
forms corresponding to mima and wahlbergi and the absence of 
such intermediates in Natal are evidence of progressive evolution 
in the Insect, and the evidence might be considered as warranting 
the conclusion that the progressive development will ultimately 
result in mzma and wahlbergi being modified into distinct species. 
The conclusion is apparently sound. In fact, exponents of the 
various theories of evolution have arrived at it over and over 
again. And yet, the systematics of di- and polymorphic species 
