196 Roger Verity 
in. as cold ones as that of northern Finland is in our times, where 
corinna and vaucheri, and to a lesser extent, also dorus, had ı 
power of evolving that wav and they had to retire southward a 
localise where conditions were suitable to their particular requir 
ments. In fact, also individually, they vary very little, as compar 
to pamphilus, showing that they are highly anabolic, and in a ve 
fixed and specialised state, uncapable of much physioiogical reacti 
to changes of surroundings. The oldest exerge fhyrsis of pa 
philus may be in comparatively similar conditions. It cannot ha 
the same hereditary factors as /yllus, or the latter would in tl 
case, produce it occasionally, at least as an extreme individı 
variety, whereas form Zhyrsides Stdg.; is its nearest approach in tl 
direction. In our times the climate of the Palaearctic region h 
evidently drifted too far from that of the tropical ones and fhyr. 
is on the verge of following its ancestors of those days ir 
extinction. The two centers of oscillation of /yllus and of pamphilus : 
now left alone to fluctuate respectively from south tho north a 
from north to south and replace each other, according to the min 
climatic variations of different Epochs. 
Exerge Iyllus, Esp. 
I have stated above that there exist no constant featuı 
proper to /pllus, by which to distinguish it from pamphilus 
an absolute way. The most useful for this purpose in pract 
is afforded by the dark marginal pattern. In /p/lus it :consists 
upperside of a premarginal streak or in a row of lunules, sh 
in outline outwardly, so that a clearly defined space of the fulvo 
ground-colour separates it from the capillary streak, which ru 
along the margin; in pamphilus it consists, instead, in one ba 
including both the streaks described above. On underside 
forewing the same premarginal band tends to be thinner a 
sharper and to have a zigzag shape in /yllus, whilst in pamphi 
it is usually obliterated or indefinite in outline. | 
The races of this exerge and their generations, as far as tl 
are known to me, are the following: 
The nymotypical form, as figured by Esper from Portug 
seems to constitute the broadspread race of the Iberian peninsu 
lt is on an average small in size and often very small. Ratl 
pale and dull in colouring on both surfaces. In the II generati 
a sharp and rather straight streak cuts across the underside 
both fore- and hind-wing, dividing the latter in two zones, of wh 
the basal one is darkened by a slight suffusion of dirty gr 
mixed with buff, and the outer one is of a clear pale buff; 
