Lepidoptera from the White Nile. 159 
places had a marvellous effect in producing intermediate 
and wet-season forms.” That the meteorological conditions 
prevailing at or about the time of emergence may in some 
cases influence the aspect of a brood appears also from 
many experiments of Mr. Merrifield, especially those with 
Selenia tetralunaria, Hufn., by which it was conclusively 
proved that for certain effects of seasonal coloration “the 
later days of the pupal period were especially important.”* 
It is worthy of notice that the rule which obtains in Precis, 
as to the superiority in size of the dry-season form, is not 
of universal application. Mr. Marshall rightly points out + 
that Mr. Barker’s statement as to the generally smaller 
size of dry-season forms is too sweeping; but there can be 
no doubt that in many instances the statement in question 
holds good. This is perhaps especially the case among the 
Pierine, concerning the Indian species of which group 
Captain Watson says:—“In all genera the dry-season 
forms are as a rule smaller than the rainy-season forms.” ¢ 
In other instances there appears to be no constant ditierence. 
The superiority in bulk of the dry-season form in 
certain species of Precis, resting as it does upon the result 
of a careful series of weighings of the two forms by Pro- 
fessor Poulton, is quite beyond doubt; but it may be well 
to remember that in other instances a difference in size may 
sometimes be more apparent than real. This may possibly 
be the case with the broods mentioned by Mr. Merrifield 
in Trans. Ent. Sog. Lond., 1892, pp. 40, 41, on which, 
together with a similar experience of Weismann’s, he 
bases a guarded opinion that both size and shape may 
be individually altered during the pupal state. This is 
a point that no doubt calls for further investigation, but 
in the meantime it will probably be allowed that, whatever 
may be the case with Precis, there is reason to believe 
that the seasonal aspect is not in all imstances deter- 
mined before the assumption of the pupal condition. It 
is, as has just been remarked, by no means certain that 
the differences in size noticed by Mr. Merrifield were as 
real as those in Pvecis, but, whether they were so or not, 
they could not under the circumstances have originated 
in the larval state.§ 
* Trans. Ent. Soc. Lond., 1891, pp. 155-167. 
tT Ibid., 1896, p. 551 ; 1895, p. 413. 
{ Journal Bombay Nat. Hist. Soc., vol. viii, 1894, p. 492. 
§ In considering the case of Precis it should not be forgotten that 
