MELANISM AND MELANOCHROISM. 295 



268), with regard to some further temperature experiments 

 conducted by Mr. Merrifield, we read : — " Mr. Merrifield read 

 a paper ' On the conspicuous changes in the markings and 

 colouring of Lepidoptera, caused by subjecting the pupse to 

 different temperature conditions,' in which it was stated that 

 the results of many experiments made on Selenia illustraria 

 and Ennomos autuvinaria, tended to prove that both the mark- 

 ings and colouring of the moth were materially affected by the 

 temperature to which the pupa was exposed ; the markings, by 

 long continued exposure before the last active changes, but 

 before the colouring of the perfect insect began to be visible ; 

 a moderately low temperature during this period causing dark- 

 ness, a high one producing the opposite effect, and two or 

 three days at the right time appearing in some cases sufficient. 

 Dryness or moisture applied during the whole pupal period 

 had little or no effect on either colouring or markings. Apply- 

 ing the facts thus ascertained, Mr. Merrifield said he had 

 obtained from summer pupse of illustraria, some moths with 

 summer colouring and spring markings, some with spring 

 colouring and spring markings, and some with summer mark- 

 ings but an approach to spring colouring. The specimens 

 were exhibited. Mr. C. Fenn, who said he did not agree with 

 Mr. Merrifield's conclusions, exhibited a very long and varied 

 series of Eiinonios autuinnarii, all of which, he stated, had been 

 bred at the same temperature. He expressed an opinion that 

 the presence or absence of moisture, rather than differences of 

 temperature, was one of the principal causes of variation." 

 The members present appear to have been of opinion that 

 Mr. Fenn's specimens, bred at the same temperature, exhibited 

 a very much greater range of variation than did those of Mr. 

 Merrifield, which were supposed to vary because of the differences 

 of temperature to which the pupas had been subjected. It 

 appears abundantly clear that Mr. Merrifield's specimens 

 would probably have varied (as Mr. Fenn's did) just as much 

 under ordinary, as they did under special conditions, and that 

 the variation in his specimens was probably due, as the varia- 

 tion in Mr. Fenn's specimens was apparently due, not to 

 temperature, but to heredity, and other incidental causes 

 combined. 



The inference suggested by Mr. Merrifield, or, more correctly, 

 the conclusion at which he arrived, appears directly opposed to 

 the inference adduced from his previous experiment on Ennovios 

 autujnnaria {Entomologist's Record, vol. i., p. 231), and I should 



