J. W. H. Harrison 205 



those between 0. autumnata and 0. jiUgrammaria and between 0. dilu- 

 taia and 0. chHstyi, invariably reappear in the ofifspring ? 



(6) If so, is this actually due to heredity and therefore germinal, or 

 is it ontogenetic, i.e. due to like environmental impulses acting anew on 

 each individual of the successive generations to produce like effects ? 



(7) If actually germinal, how do the differences arise and how are 

 they fixed ; are we concerned with " germinal " mutation or with acquired 

 characters depending on the prolonged action of environmental agencies 

 and their final registration in the germ cells with subsequent inheritance ? 



(8) Are the current explanations of melanism in the Lepidoptera in 

 harmony with the facts ; and what evidence has the genus Opwabia to 

 offer on the subject ? 



(9) In all of the problems enunciated how far has " natural" selection 

 played its part ? 



By a perusal of the above questions it will be seen that I undertook 

 the work without allowing my natural bias against the Lamarckian 

 position to prejudge the case; what answers I obtained to them will be 

 discovered in the succeeding pages. 



II. Variation — Subspecies — Local Races — Melanism. 



(a) General. 



In the introductory remarks I indicated that the genus Oporabia 

 included two species and two subspecies, 0. autumnata with its subspecies 

 0. filigrammaria, and 0. dilutata with 0. christyi. It now behoves us 

 therefore to consider the exact relationship, if such consideration is 

 possible, between these pairs of forms, and incidentally to assure our- 

 selves of the value to be attached to the term subspecies. 



In my earlier work I was always sceptical of the existence of such 

 things as subspecies and shrank from using the word. Prolonged study 

 of the present genus has considerably altered my views in this respect, 

 so that I have come to recognise the existence of such entities as 

 exceedingly probable, and in any case the use of the word as justified. 

 In Oporabia the two subspecies recognised, when assessed at their true 

 value, do not depart very widely from the Jordanian concept of the 

 " little species," or, as I have usually called it, the " microgene." Further- 

 more, the probable course of development of Oporabia filigrammaria 

 gives us some hint that such subspecies or microgenes may have arisen 

 by a long period of isolation not in itself of sufficient duration or of such 

 a type as to allow of divergences of full, unchallengeable, specific value. 



