THE NEW ENTOMOLOGY. 187 



from use and disuse of functional attributes, as well as from 

 external influences; and he shows that in the social Hymenoptera 

 one set of differences in structure and instinct is determined by 

 nutrition before the egg is laid, and a further set by nutrition 

 after the egg is laid. And further, from the partial and in other 

 cases total abortion of the hind limbs of whales, towards which 

 result no defect of nutrition can be alleged as cause, he argues 

 that Professor Weismann's theory of "panmixia" affected by 

 selection is inadequate to account for more than the partial 

 suppression of the hind limbs of cetaceans, but that it must be 

 the result of the disuse of those appendages, together with the 

 inheritance of characters so acquired. 



The modern school of entomologists generally appears to 

 lean strongly towards the latter school of thought, often perhaps 

 overshooting the mark by referring all variations to the im- 

 mediate action of present environment. It seems probable that 

 if more attention were paid to insular fauna, some of these 

 problems might find solution. 



A more careful and accurate study of Irish insects, for 

 instance, seems most advisable. Mr. Nicholson's thoughtful 

 and valuable paper on Corsican butterflies, which follows that of 

 Mr. Sharp (p. 116), is very suggestive in this respect. Ex. gr., 

 it would be interesting to learn if the phenomena of Vanessa 

 urticce var. ichniisa being restricted to a single brood in a climate 

 possessing a summer of so long duration may be accounted for 

 by the fact that the food plant is well known to be scorched very 

 early in the year by the powerful sun of Corsica. Also whether 

 the species is perpetuated by the long-lived female imagines sur- 

 viving the whole summer (perhaps aestivating ?) and winter, or 

 whether a portion of the pupae are delayed in emergence. 



That the larvae are to be found through a considerable period 

 {teste Mr. Nicholson) is probably due to the insufficient nutriment 

 afforded by the withering food plant, as well as by its irregular 

 survival in moist and shaded spots. These observations bear out 

 Mr. Sharp's remarks as to the necessity in future of restricting 

 somewhat the scope of individual labours in the entomological 

 field. To solve such problems as have been alluded to, we 

 require the aid of patient and continuous investigation into the 

 particular facts of each case ; and there is ample witness of the 

 increase of scientific students who are contented to limit their 

 enquiries to special groups of phenomena. To such all honour 

 is due. 



