{ xxxvi ) 



Geometridce possessed the power of colour adjustment. Mr. 

 F. Merrifield, the Rev. J. Seymour St. John, and Mr. Jacoby 

 took part in the discussion which ensued. 



Papers read. 

 Mr. F. Merrifield read a paper entitled "The effects of 

 temperature in the pupal stage on the colouring of Pieris napi, 

 Vanessa atalanta, Chnjsophayius phlccas, and Ephyra piinctaria." 

 The author stated that some of the artificial temperatures to 

 which he had subjected pupre in the course of these experiments 

 corresponded to natural ones, though, in most cases, in a 

 necessarily incomplete manner; natural temperatures were 

 so fluctuating that it was difficult to imitate them artificially, 

 but he did not think the difference was for his purposes an 

 important one, for in many instances he had used both 

 artificially equable and naturally fluctuating temperatures, 

 and in these cases he had found that a fluctuating tem- 

 perature produced results similar to those obtained from an 

 equable temperature corresponding to the mean of the 

 fluctuating one. In reference to the known English mean 

 temperatures of the spring and summer months, it must be 

 borne in mind that these are shade temperatures, and are 

 below, and, under certain circumstances of exposure or 

 absence of cloud, considerably below, those to which objects 

 exposed to both sunshine and shade, under natural con- 

 ditions, would be subjected. He would also premise that in 

 his experiments the pupse were exposed to the different tem- 

 peratures, in nearly all cases, within a day or two, and often 

 within a few hours, after pupation. Pupte of the summer 

 emergence of P. napi, iced (/. e. at 33° F.) for from three to 

 four months, and then subjected to the temperature of 

 spring, at which they emerged in five or six weeks, showed 

 most but not all of the characteristic features of the spring 

 emergence ; those plunged at once from the artificial winter 

 into the temperature of a very hot summer, emerged in six 

 days, and were intermediate in most of their features. The 

 summer pupae of this species, or a portion of them, were 

 very apt to go over to the spring, and, when so disposed, 

 the subjecting them for many days to a forcing temperature 



