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 he'^i 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 

 lew 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 liis 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 

 I am now referring. 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 fonn 

 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 ! " 



