( cv ) 



the effect of subjecting the insects dui-ing their immature 

 stages to abnormal conditions of temperature and humidity. 



He pointed out that the members of a brood which had been 

 reared under ordinary conditions as larvae, but had been ex- 

 posed as pupje to damp heat, showed on emergence little or no 

 difference from those examples that had been reared under 

 normal conditions throughout. The emergences took place in 

 June 1905, and the resulting butterflies were of the usual 

 dry-season phase, though less markedly dry-season than a pair 

 captured in the field at the same date. 



On the other hand, several examples, belonging to one 

 brood, had been brought up as larvae in an atmosphere of damp 

 heat, from which they were removed on pupation into natural 

 conditions. The resulting butterflies, emerging in July during 

 the height of the dry-season, were on the .upper-side almost of 

 the wet-season phase, while others of the same brood which 

 had been kept in damp heat throughout both the larval and 

 pupal stages went still further in the same direction. Some of 

 these latter indeed, especially the females, showed on the upper 

 surface the wet-season pattern fully developed. On the under 

 surface the approximation to the wet-season phase was some- 

 what less complete ; the most advanced examples of the effect 

 of exposure to damp heat during both preliminary stages 

 still exhibiting beneath some slight trace of the dry-season 

 mottling. On the whole, however, very little difference was 

 apparent between these artificially-produced wet- season forms 

 and specimens which were shown of the normal wet-season 

 phase captured in the open before the cessation of the rains. 



Dr. DiXEY further remarked that Mr. Marshall was to be 

 congratulated on having been the first to produce, in tropical 

 species of Pierinx, results as definite and unequivocal as any 

 of those obtained by the President, Staudfuss, Fischer and 

 others in European lepidoptera. Mr. Marshall had conclusively 

 shown in the case of the present species that the natural 

 stimulus for the assumption of the wet-season phase could be 

 successfully imitated under artificial conditions ; he had also 

 proved experimentally that while both preliminary stages were 

 to some extent capable of reacting to external conditions, by 

 for the most susceptible period must be contained within the 



