146 INSECTS AND HEREDITY 



originally determined it. In opposition to Lamarck, one 

 must urge, in the first place, that this thing has never 

 been shown experimentally to occur ; and in the second 

 place, there is no ground for holding its occurrence to be 

 probable, but, on the contrary, strong reason for holding 

 it to be improbable. Since the old character (length, 

 breadth, weight) had not become fixed and congenital 

 after many thousands of successive generations of in- 

 dividuals had developed it in response to environment, 

 but gave place to a new character when new conditions 

 operated on an individual (Lamarck's first law), why 

 should we suppose that the new character is likely to 

 become fixed after a much shorter time of responsive 

 existence, or to escape the operation of the first law ? 

 Clearly there is no reason (so far as Lamarck's statement 

 goes) for any such supposition, and the two so-called laws 

 of Lamarck are at variance with one another.' 



These passages have been quoted at length because 

 they apply not only to the thoughts 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 law 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 V 



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 



1 Nature, vol. li, 1894, p. 127. 



