22 
ABERRATION 
providing the caterpillars from the same batch of eggs are 
all reared under precisely similar conditions, and assuming 
that the batch of eggs numbers 900, and of these 850 attain 
maturity, pupate and produce 850 butterflies, all but a single 
specimen, i.e. 849 may be absolutely normal in every respect, 
yet the one odd example may be so dissimilar in appearance 
as to suggest its belonging to a widely-distinct species. 
As this particular abnormal phase tending to melanism, 
always of rare occurrence, turns up occasionally in remotely 
separated localities throughout the country and is not due 
to climate, food, etc., it can only reasonably be assumed that 
it is a reversion to a primitive ancestral form. Otherwise 
the question remains : What are the latent forces existing 
to reproduce at distant dates and in distant localities perfect 
copies of a certain aberrant type entirely distinct from the 
normal species ? 
