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XVI. Mr. Merrifield’s Experiments in Temperature- 
Variation as bearing on Theories of Heredity. By 
Freperick A. Drxey, M.A., M.D., F.E.S., Fellow of 
Wadham College, Oxford. 
[Read March 14th, 1894.] 
Tue results of Mr. Merrifield’s experiments on the varia- 
tions produced in butterflies by the exposure of the pupa 
to different conditions of temperature, are in themselves 
of great interest. But the interest becomes enhanced 
when it is recognized that many of the new features 
which make their appearance under these conditions are 
identical with those occurring normally in other species 
more or less closely allied to the subjects of experiment ; 
that in not a few instances the disturbance of natural 
temperature-conditions appears to have caused reversion 
to an earlier stage in the phylogenetic history of the 
species; and further, that the ancestral.features thus 
revived seem to vary with the nature of the disturbance. 
Examples of these phenomena, from a previous series 
of experiments, were given in ‘Trans. Ent. Soc. Lond. 
1898, p. 55, and were commented on by me (Ibid. p. 69). 
The latest results obtained by Mr. Merrifield, besides 
confirming many of the former, furnish further instances 
of the same nature, as follows :— 
I. VANESSA ATALANTA. 
A. Warmed. 
(1) The occurrence of red scales in the dark ground- 
colour between the middle of the scarlet band and the 
large white costal spot c. This is an approach to the 
condition in V. huntera and V. myrinna, and more 
remotely to that in Grapta and Argynnis. A correspond- 
ing feature is seer in V. to, which in this respect is 
more ancestral than V. atalanta. 
(2) The tendency towards the formation of a scattered 
ring of red scales round the spots 8 and ¥y of Series D. 
TRANS. ENT. SOC. LOND. 1894,—parT III. (SHPT.) 
