(| ixxvne ) 
from indulging in any speculative disquisition on my own part, 
because, however attractive to myself such a course might be, 
I very much doubt if, in the present very restricted bounds 
of our knowledge, it would prove of any service to the 
Society. To generalise or to speculate to any good purpose 
demands a considerable body of well-ascertained fact as a 
basis, and this—as my remarks have shown—is precisely what 
is wanting in the present instance, notwithstanding the 
labours of the entomologists of distinction to whom reference 
has been made. ° While fully recognising that the artificial- 
temperature experiments noted above have been designed and 
conducted with a skill and thoroughness truly admirable so 
far as certain species of Palearctic and Nearctic Lepidoptera are 
concerned, it cannot at the same time be denied that even in 
Europe very little has been done to ascertain all the natural 
conditions under which seasonal dimorphism occurs, or to 
what extent it is adaptive to the environment; and when 
we turn to the wide tropical and subtropical regions, it 1s 
obvious that we stand upon merely the threshold of inquiry. 
We have, indeed, from these regions—thanks to such capable 
observers as De Nicéville and Marshall—some valid experi- 
mental evidence to guide us, but this must be very greatly 
added to, and the life-history of the dimorphic species. be 
worked out from many different directions, before we can 
hope to approach to a clear comprehension of the complex 
problem now presented by the extraordinarily impressionable 
and mutable lepidopterous organism. In studying the cases 
under notice, it is impossible not to recognise that the most 
diverse influences are at work,—indications of protective and 
mimetic adaptation, and of sexual selection as well, being com- 
bined or contrasted with the effects of varying temperatures 
and degrees of atmospheric humidity, and with distinct ten- 
dencies in the direction of reversion to ancestral characters. 
The investigation is one to tax the insight and resource of 
the ablest and most zealous naturalists, and demands unre- 
mitting and most exact observation and record, with carefully 
controlled breeding from the ova for many successive genera- 
tions, during a considerable series of years. I am as fully 
persuaded now as I was on the occasion of my last year’s 
