92 THE entomologist's record. 



held to be the cause of the variation observed, for variation it un- 

 doubtedly was, unnatural variation. In this direction the V. urfi'cce 

 were a strong case in point. In conclusion Mr. Fenn stated that the 

 deduction he drew from these experiments and from comparing the 

 results with his own experiences, were as follows, viz. : Such variation 

 as shown by Mr. Merrifield is practically impossible in a state of nature 

 unless we assume it to be the result of disease, and as such a condition 

 would weaken the brood to a great extent, it would all the more rapidly 

 disappear, and in any case would fail to compete with healthy broods 

 in the struggle for existence. However, he said, we may differ with 

 regard to these experiments, we must all admire the way in which they 

 have been carried out, and he begged to propose a very hearty vote of 

 thanks to Mr. Merrifield for his paper. After Mr. J. Jenner Weir had 

 made some remarks bearing on the cause of such colour variation as 

 was referred to by Mr. Merrifield, and its relation to surplus energy, 

 several members (called on by the President) spoke at, rather than 

 about the subject, and it seemed very doubtful whether some of them 

 had read Mr. Merrifield's papers relating to his experiments. Mr. Adkin 

 got back to the question, and gave an account of some Vanessa urticoi 

 bred by him, which tended to support Mr. Merrifield's facts, especially 

 with regard to the development of the blue lunules. Mr. Tutt stated 

 that he had already suggested explanations of many of Mr. Merrifield's 

 results in his pamphlet on Melanism and Melanochroism in British 

 Lepidoptera, and within the last few weeks in the Introduction to vol. 

 ii. of The British Noctuce and t/ieir Varieties. Mr, Tutt maintained 

 that on broad grounds there was no doubt that heredity and other 

 factors inherent in the species explained some of the results, whilst 

 exposure to moisture and other ordinary climatic changes helped to 

 explain others. But there was at the same time no doubt that tempera- 

 ture did more or less affect the coloration. The question at issue was 

 now reduced to its narrowest possible compass, and he asked. How does 

 temperature affect the coloration of lepidoptera? Is the action direct 

 or indirect ? He had no doubt himself that such result was entirely 

 indirect, and that its action was due to its influence on the constitu- 

 tion ot the pupa, the pupa being taken by Mr. Merrifield as the stage 

 in which the most vital changes in colour were affected. Mr. Tutt 

 pointed out from Mr. Merrifield's own showing that " the larva must by 

 no means be overlooked " in the question ; but, restricting himself to 

 the pupal stage, he would attemi)t to explain how the changes on Mr. 

 Merrifield's experiments were brought about. He would distinguish 

 particularly between the butterfly, Vanessa urticce, and the moths, 

 Selenia, etc. In the first case, crippling was so apparent, that no one 

 could argue for a moment that " disease," or a failure to carry out the 

 normal processes of development, might not be a potent factor, and 

 there was no doubt it was. Shortly, he assumed, that when the larva 

 was full-fed it had a certain amount of " surplus " energy stored up, 

 which, elaborated under suitable conditions, would become the 

 normally coloured pigment. Prevent by artificial condition (tem- 

 perature, etc.) the proper elaboration and consequent formation of 

 this pigment, and the result would follow that the imago would 

 exhibit the result of such action on emergence. But the ground 

 colour of V. urticce is essentially black. Therefore the failure to 



