significance of the varvations, cc. 73 
Assuming this to be the case, we may perhaps explain 
the results arrived at by Mr. Merrifield with V. atalanta 
as follows :— 
The warm ‘‘callirrhoé”’ stage is more recent than the 
cool ‘‘blue-centred’”’ stage (see above, p. 71). The 
normal V. atalanta, though still more recent than the 
“callirrhoé”’? form, shows in some respects a kind of 
atavism, skipping the ,“‘callirrhoé”’ stage, and reverting 
in certain points (e. g., the white spots on the fore wing, 
and the blue about the anal angle of the hind wing) to 
an earlier one. By the subjection of the pupe to a 
sufficient amount of cold, the moderate atavism of the 
recent V. atalanta may be rendered more pronounced ; 
while the substitution of heat at the same time both 
checks the atavism and encourages reversion to a more 
immediate ancestor. In other words, the normal V. 
atalanta may be warmed back towards P. callirrhoe, or 
cooled back still further towards the “‘ protovanessa.”’ 
