( xciv ) 
fresh stage of growth in our comprehension of at least one 
portion of the evolutionary domain. And the peculiar value 
of entomological data for research on Darwinian lines was 
speedily recognised. The material with which we entomo¬ 
logists have to deal is for the most part abundant, of manage¬ 
able size, easy of manipulation, and favourably constituted for 
experiment. Hence it has followed that many of the most 
important steps in the progress of our evolutionary knowledge 
have depended directly or indirectly on the study of insects. 
Let me take as an example the present state of scientific 
opinion with regard to the transmission of acquired char¬ 
acters, or, as some prefer to put it, the inheritance of somatic 
modifications. It is hardly necessary for me to say that 
neo-Lamarckians are still on the look-out for an instance of 
such transmission, and that neither among insects nor any¬ 
where else have they been able to find one. The antecedent 
improbability of the alleged phenomenon has been well 
shown by many writers, and by none more convincingly than 
by Professor Poulton, in one of the admirable Presidential 
Addresses delivered by him from this Chair. But the failure 
of the neo-Lamarckians to establish the principle of specific 
transmission must not blind us to the fact that the germ- 
plasm is far from possessing the stability and inviolability 
with which it was once supposed to be endowed. Weismann 
himself, with great candour, admitted at a comparatively 
early stage in his work that the germ-plasm was not in all 
cases out of the reach of external influences. It is of special 
interest to us as entomologists that he was led to this 
conclusion by experiments on a butterfly—the well-known 
“Copper” {Chrysophanus phlaeas). Exposing pupae of the 
northern golden-red form of this insect to an abnormally 
high temperature, he found that many of the resulting 
butterflies were slightly dusted with black. On the other- 
hand, pupae bred from eggs sent from Naples, which would 
under ordinary circumstances have produced butterflies of the 
dark southern summer form, were subjected to a relatively 
low temperature and gave rise to perfect insects in which the 
normal dark coloration was sensibly diminished. These 
results, as we shall doubtless all remember, agree with those 
