1)2 Mr. Merrifield's incidental ohseroations 



Weismann's experiments show the pupal stage to be 

 one sj^ecially affected by temperature. The subject is 

 too considerable to be discussed here, but I venture to 

 point out that two features associated with seasonal 

 dimorphism, viz., the important one of size, and, as it 

 would appear from Mr. W. H. Edwards' experiments, 

 the very important one of shape, are determined in the 

 larval stage ; and that in the three species experimented 

 on by me the larval stage was in fact much sitortened by 

 the high temperature applied (see this paper, passim, 

 also Trans. 1888, pp. 130, 131, 132—3) ; whereas in those 

 experimented on by Prof. Weismann the larval period is 

 stated to have been very little shorter in one brood than 

 in the other, so that the duration would not, — and, it is 

 indeed stated, did not, — engage attention (Weismann, 

 by Meldola, p. 10).] Though kept at a forcing tem- 

 perature, none emerged until 11th November, a period 

 of more than 2 months ; a second appeared on the 12tli 

 November ; and 5 more appeared between the 9th and 

 26th December. Six of the seven were cripples, and all 

 the 7 were of the summer type, but duller in colour, and 

 the latest of the 7 are no darker than the earliest. On 

 7th November, after gradually cooling them down for a 

 fortnight, I put 10 pupae out-of-doors, where they had a 

 good deal of frost before they were brought indoors on 

 1st January, a period of 9 weeks. One had come out in 

 the interval, and another appeared 3rd January. From 

 the 9th they were forced, and 4 more appeared between 

 22nd January and 28tli February. x\U 6 were distinctly 

 of the dark spring type, though rather poor in colouring, 

 and 3 were cripples. In this case a marked effect seems 

 to have been produced on the colouring of the moth by 

 exposing the pup^e to a freezing temperature, [and no 

 such effect produced by considerable retardation without 

 cooling.] 



I mentioned some pupjE which Mr. Jenner had, and 

 which, with the exception of 2, would evidently have 

 l)een single-brooded had they not been subjected to 

 artificial treatment. He kindly lent half of them, 

 consisting of 10 males and IG females, to me, and on 

 10th September, 1888, I pla-.^ed them in a forcing-box, 

 which was kept at 75° — 80^, except for the first fortnight 

 in Octoljer, when, for reasons connected with another 

 ex[ieriment. it stood at 00^ — 65". Nine emerged, all 



