25 
been reared from backward caterpillars collected by him in the 
autumn, and that he had delayed the appearance of the perfect 
insects by keeping the chrysalids in an ice house.” 
This statement, taken in connection with the fact that the 
summer brood of the purple thorn could be made to yield either a 
second summer brood or a spring brood at will, by merely hasten- 
or delaying the appearance of the perfect insect, induced me to 
suggest, in some notes on ‘ Variety Breeding,’”” which I was writ- 
ing in the ‘‘ Entomologists’ Monthly Magazine” in 1867, that the 
power of hest and cold to modify the perfect moth or butterfly 
should be patiently and practically investigated. My remarks 
created some stir at the time, and Dr. Jordan, one of the best 
entomologists of the day, expressed a hope that experiments would 
be made, and the results (negative as well as positive) published. 
Still nobody seemed to rise to the bait, till some fifteen or 
twenty years ago Mr. Merrifield, of Brighton, took up the matter 
seriously, and by a course of experiments extending over many 
years, has arrived at startling results, the publication of which has 
made his name famous throughout the entomological world. The 
Germans, too, as well as Swiss, Canadians, and Americans, have 
entered the field, and an excellent paper on the subject, by Dr. 
Standfuss, of Zurich, has been translated, and is now being pub- 
lished in the pages of the ‘‘ Entomologist.”’ This latter, so far as 
it goes, corroborates the results obtained by Mr. Merrifield in a 
remarkable way, and it is plain that though comparatively very 
few species have yet been submitted to the action of heat and cold, 
this method of investigation will prove very valuable in elucidating 
many points connected with the origin of species and other knotty 
subjects. In his paper, Dr. Standfuss remarks: “I can truly say 
that during the period of more than 25 years which I have devoted 
to practical biological studies in entomology, I have never had 
before me anything approaching the astonishing results to which 
Tam now reierring. Can it be called anything but astonishing 
that it shoold be possible, by means of a simple experiment, to 
make caterpillars of the swallow tail butterfly, collected at Zurich, 
develop into a form of perfect insect such as that which flies in 
August in Syria! . . . . Or that from German and Swiss 
chrysalids of the Camberwell Beauty, by the action of well defined 
factors, there should be produced a butterfly which in part comes 
very near the Mexican form! Or to force at will one half of the 
progeny of one and the same Painted Lady to develop into a form 
of perfect insect almost identical with that occurring in German 
Africa, and the other half to assume an aspect like that occurring 
at the northernmost limit of its range, as, for instance, in 
Lapland!” 
