(8h) [xiii 
the latter the larval was proved to be the susceptible period, 
exposure of the former to damp heat in the larval condition 
produced no perceptible effect, the resulting emergences being 
of the ordinary dry-season phase. Exposure, however, to the 
same conditions in both larval and pupal stages resulted in a 
transformation to the full wet-season form. In this species 
the seasonal changes chiefly affect the under-surface. 
A further point of great interest received illustration from 
the same series of bred B. severina. This was the difference 
in effect between moisture accompanied by heat and moisture 
alone. Those individuals exposed as both larve and pupz to 
the combined effect of heat and moisture, emerged, as has been 
said, in the full wet-season condition. Those, on the other 
hand, exposed in both these stages to moisture alone without 
heat, emerged with the ground-colour of the hind-wing under- 
side characteristic of the wet season, while the dark veining of 
the dry season was in the same specimens not only present 
but strongly accentuated. It might be said, in fact, that the 
employment of moisture only, without heat, had produced a 
well-marked form, unknown under normal conditions in this 
region, though occurring naturally in some other parts of 
Africa, as Uganda and Natal. 
To sum up: Mr. Marshall by means of these carefully con- 
ducted experiments had shown that in the two species of 
Teracolus, T. omphale and T. achine, a brood which left to itself 
would produce the dry-season phase of the imago, might by 
the application of heat and moisture be made to assume the 
characteristic features of the wet-season form. Further, in 
each of these cases it was shown that exposure to the artificial 
conditions during the larval stage only was capable of produc- 
ing nearly the whole effect, the result of similarly treating the 
pupa only being scarcely perceptible. 
On the other hand, while in Belenois severina an equally 
complete transformation from the dry- to the wet-season form 
had been accomplished, it was clearly shown that in this case 
the larval was not the susceptible stage, the result of exposing 
the larva only to the artificial conditions being practically nil. 
In this species also Mr. Marshall had experimentally disso- 
ciated the two conditions of heat and moisture, showing that 
