208 Dr. F. A. Dixey on 



"No notes were kept of individual inarkings, but on 

 comparing the tliree sets it was noticeable, as in previous 

 experiments, that considering the disparity of conditions, 

 the markings showed wonderfully little difference. It is 

 however indisputable that, taking the specimens in con- 

 junction with those of the previous experiment, all those 

 subjected to dry heat had the black markings appreciably 

 less developed than those whose jjupa? were kept in a cool, 

 moist atmosphere. Those that were reared entirely in the 

 breeding-cage are mostly of an intermediate type of 

 colouring, though two are quite as bright as the heated 

 specimens, but none of them resemble those that were 

 kept damp. 



"It is noteworthy that in Crcnis hoisduvcdii the speci- 

 mens reared under normal conditions showed just the 

 opposite tendency. 



" Although the experiments are on far too small a scale 

 to j^i^ovc anything one way or the other, yet to my mind 

 they appear to lend more support to the theory that the 

 heavier development of black markings in South African 

 butterflies during the summer is probably more dependent 

 on the prevalence of moisture than on the action of heat : 

 though the very small effects shown by these agents in the 

 above experiments suggest the supposition that the absence 

 or presence of black markings alone cannot be referred 

 entirely to climatic agency, as I had been previously 

 inclined to think, but have been developed by natural 

 selection, for some purpose not at present apparent, which 

 has worked on the slight tendency to variation caused by 

 climatic influence." — G. A. K. M. 



In 1896 Mr. Marshall had exposed some larvae of Acrma 

 anacreoyi to "dry-season " conditions just before pupation, 

 but they all died in consequence, as he believes, of over- 

 heating (Estcourt, Oct. 15, 1896). On Oct. 7, 1897, he 

 writes from Malvern : " The experiment in which I found 

 that the pupae of Acr/ea cabira were killed by dry heat 

 which did not affect Terias hrigitta, leads me to think 

 some of these highly-developed nauseous species may have 

 suffered in hardness of constitution, which would account 

 for their not spreading more widely than they do." 



Of the specimens referred to by Mr. Marshall in the two 

 series of experiments on Pinacopteryx 2ngeci, Boisd., a, c and 

 e of the first series, and a, h, d, c, f and h of the second 

 series are in the Hope collection. The divergences noted 



