(xi) 
species. His researches extended besides to upwards of twenty 
monomorphic ones; they were carried out with admirable 
skill, care, and exactness of record, and the resulting 
phenomena—especially in the species of Vanessa—were not 
only most remarkable in themselves, but also, as disclosing 
apparently ancestral characters, of the deepest interest in 
their bearing on the phylogeny of the species concerned. The 
latter aspect of these investigations has been ably dealt with 
by Dr. F. A. Dixey, who, in his published comments on Mr. 
Merrifield’s papers of 1893 and 1894,* points out that they 
seem to go far towards indicating the possibility that a dis- 
turbance of natural temperature conditions, whether in the 
direction of heat or cold, can produce in a monomorphic 
species a tendency towards reversion, and also notes the pro- 
duction by these experiments of ancestral features in Vanessa 
io, V. polychloros, and Grapta C.-album. 
Concurrently with Mr. Merrifield’s later work appeared 
both Dr. M. Standfuss’s f and Prof. Weismann’s { important 
memoirs, containing accounts of the series of temperature 
experiments carried on by them respectively in the course of 
‘the last decade. Standfuss’s paper of 1894 deals with the 
effects of the warm and cold treatment of the summer pup 
of nine species of European butterflies. None of these can be 
included among seasonally-dimorphie species in Europe itself, 
but the author points out that the effect of heat on the 
Ziivich pup of Papilio machaon was to produce specimens 
perfectly resembling the August form of the species that is 
found in Syria. Other striking results as given by the 
* See Dr. Dixey’s papers (1) ‘‘ On the Phylogenetic Significance of the 
Variations produced by difference of Temperature in Vanessa atalanta”’ 
(Trans. Ent. Soc. Lond., 1893, p. 69); and (2) ‘* Mr. Merrifield’s Experi- 
ments in Temperature Variation as bearing on Theories of Heredity.” 
(Op. cit., 1894, p. 439.) 
+ ‘* Ueber die Griinde der Variation und Aberration des Falterstadiums 
bei den Schmetterlingen,” 1894. (Engl. transl. by Dr. F. A. Dixey in 
** Entomologist,’ 1895.) 
‘¢ Handbuch der Paliarktischen Gross-Schmetterlinge fiir Forscher und 
Sammler,” 1896. 
+ **New Experiments on the Seasonal Dimorphism of Lepidoptera ”’ 
(1895). Engl. transl. by W. E. Nicholson in ‘‘ Entomologist,” 1896. 
