Lepido'ptcra from tlce White Nile. 159 



places had a njarvellous 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 f 

 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 

 Pierinm, 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 difference. 

 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. Soc. 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 instances 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 Precis, 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. 



t Unci, 1896, p. 551 ; 1895, p. 413. 



X Journal Bombay Nat. Hist. Soc, vol. viii, 1894, p. 492. 



^ In considering the case of Precis it should not be forgotten that 



