426 Mr. F. Merrifield on Temperature Heperiments 
subjected, adding that the spring emergence appears 
to be less sensitive than the summer emergence is to 
temperature. Neither of the broods experimented on 
by me has proved so sensitive as those operated on 
by Prof. Weismann, and described by him (“Studies in 
Heredity ”’). 
Pararge egeria. This insect has two well-known climatic 
forms, the light spots in the South Kuropean form 
having the bright ochreous colouring of P. megera, 
instead of the straw colour of the English var. 
(egerioides). But the experiments tried afford little or 
no reason for supposing that these differences in appear- 
ance are the direct result of temperature. 
I obtained, between the 25th May and the middle of 
June, more than one hundred pup, which were sub- 
jected to various temperatures from between 80° and 
90° down to 33° (for many weeks), with various trans- 
fers from the lower to the higher temperatures. 
The chief difference, in general appearance, is between 
Classes I. and II. (forced) on the one hand, and Classes 
IV.-XIV. (those at 56° and under). ‘The former have 
the light spots smaller and less clearly defined, and the 
dark ground colour considerably lighter, and im many 
cases freckled with small dark brown spots. Class III. 
(open air, at about 66°) are not quite so dark as Class 
TV., but much nearer to them than to the forced. 
Though the light spots in those forced are smaller 
than in the others, they are somewhat more numerous. 
Class VIII. (iced and then forced) have the ground 
colour dark, but the light spots as numerous as in those 
which were forced, and as large as are the spots in those 
at the lower temperatures. One of these indeed, which 
I exhibit, has an inner row of light spots or traces 
of them on the secondary wings in nearly all the 
interspaces, and on the underside a perfect submarginal 
chain of six light spots, pupilled with dark brown, ona 
light ground colour. 
A few examples I reared from eggs laid in August 
showed the same effects generally as those from the 
eggs laid in April and May, so that there does not 
appear to be any marked constitutional difference in this 
respect between the spring and summer emergences of 
this species; my experiments would, however, lead me 
to expect those which emerge in spring to be in general 
