( ix ) 



opportuuity. Although he disagreed with Col. Manders' opiniou 

 on this point, he wished, in concluding his remarks, again 

 to congratulate him on the solid results he had obtained and 

 shown to the meeting. 



The Rev. G. Wheeler challenged the position referred to in 

 the paper that, because shock has been shown in some cases to 

 produce atavistic results, there is anything inherently improb- 

 able in its producing in other cases an impetus in the direction 

 in which development is tending. He maintained that this 

 might be expected to depend on two factors, one internal the 

 other external to the organism affected ; first whether the 

 organism subjected to the shock had reached a stage in which 

 the tendency to new development was stronger than the 

 atavistic tendency, and secondly whether the nature of the 

 shock was in the direction of the forces (whatever they might 

 be) tending to produce the newer form, or in the direction of 

 those tending to check such development. 



Mr. Merrifield said that his experiments on Rumicia phlaeas, 

 to which Col. Manders had referred, were on the pupae, not the 

 larvae. He had not at that time realised, as he had done 

 since, the important effect of temperature in the larval stage. 

 Applied to pupae it had an effect on the general colouring of 

 the imago, very marked in the case of many of the " Thorn " 

 moths, and other Geometridae ; a high temperature in the 

 later part of the pupal stage tended to produce a chestnut 

 colouring, verging on orange, a low temperature, darker 

 colouring approaching chocolate. But in these species, which 

 were double-brooded, and in the double-brooded butterfly 

 Araschnia leoana, the most complete effects, not merely in 

 colouring but in habits, were produced in the larval stage, 

 and especially in its earlier instars ; larvae of either of the 

 two broods of A. levana could thus all be converted by the 

 appropriate temperature into the other seasonal form — into the 

 winter phase with its long fixed pupal period, producing in 

 spring a butterfly resembling in appearance a small " fritillary," 

 or into the summer phase (prorsa) with its very brief pupal 

 period, resembling a small L. sihylla. As regards " shock" it 

 appeared to be in favour of that view that when the tempera- 

 tures to which the pupae were subjected were extreme — below 



