Crear |) 
apply not only to the thought of Lamarck but to those of 
many modern naturalists as well, and because, so far as I am 
aware, no attempt has been made to meet the objection. In 
its most condensed form the argument may be stated thus :— 
Lamarck’s “ first Jaw assumes that a past history of indefinite 
duration is powerless to create a bias by which the present 
can be controlled ; while the second assumes that the brief 
history of the present can readily raise a bias to control the 
future.* 
I now pass to the discussion of evidence derived from 
the study of the insect world. 
I do not propose to multiply examples, but shall be content 
with a few of those which seem sufficiently well adapted to 
illustrate the main lines of evidence. They have been chiefly, 
but by no means invariably, selected from the Lepidoptera. 
This is merely due to the accident that my experience has 
been chiefly gained in this Order, and not because the examples 
are in any way more suitable or convincing than those of other 
Orders. As regards the most interesting part of the discussion, 
that relating to instinct, the most striking examples have of 
course been chosen from the Hymenoptera. 
The origin of the pupal groove which receives the silken loop 
in Pierine, ete—If we examine the dorsal surface of such 
a Pierine butterfly as Pieris brassice or rape it is at once 
seen that the first abdominal segment is traversed by a strongly 
marked line parallel with its posterior boundary. ‘This 
character is so well marked that it presents all the appear- 
ance of a morphological feature. 
A study of the living suspended pupa shows that the line 
is formed by the approximated lips of a groove which receives 
the silken loop or “‘girdle” as it is often called. Longitu- 
dinal vertical sections of the dorsal cuticle are of course 
transverse to the line, and reveal the fact that the bottom 
of the groove is specially thickened. Here was a feature at 
first sight strongly suggestive of the mechanical effects of 
linear pressure, pointing to an origin in a kind of mutilation 
performed by the silken cord upon the soft freshly-exposed 
surface of the pupa. When I found that removal of the loop 
* “* Nature,” vol. li, 1894, p. 127. 
