i 5 2 INSECTS AND HEREDITY 



been subjected to the strain of gravity and has responded 

 by the production of a definite shape, viz. one in which 

 the long axis is parallel with the line of force. And yet 

 not a trace of any hereditary effect is manifest. Remove 

 the strain and the individual is free, unbiased by the 

 forces exerted upon unnumbered ancestors, to assume 

 an entirely different shape. 



Vanessid pupae alone, so far as I am aware, have 

 been studied from this point of view. Figures of other 

 suspended Nymphaline pupae, however, indicate that all 

 do not yield equally to the strain, although I believe 

 that all are to some extent affected. The pupae of 

 the Argynnidae (the ' Fritillaries ') contrast in an interest- 

 ing manner with those of the Vanessidae in this respect. 

 The strongly-curved pupa of Argynnis aglaia figured by 

 W. Buckler 1 was probably supported wholly or in part 

 by a leaf, as is suggested not only by the shape but the 

 plane of the surface of attachment, as shown in the figure, 

 and to some extent by the description. 



Variable Protective Resemblance in Insects. 



The power which it is now known that many larvae 

 and pupae possess of changing their colour into corre- 

 spondence with the tints of each one of several possible 

 environments has been thought to favour the Lamarckian 

 interpretation of the origin of variation. Thus the late 

 George J. Romanes said of the evidence which had been 

 brought forward to prove the power in question : ' It 

 has always appeared to me that the experiments them- 

 selves are among the most valuable which have hitherto 

 been made regarding the causes of variation ' ; 2 an 

 opinion due, as the writer states, to his acceptance of 

 the ' Lamarckian conception '. 



On the other hand, I have never doubted that the 

 results are in the nature of a climax rather than a founda- 

 tion, that they represent the highest achievement of 

 Natural Selection in the protective colours of insects. 



1 Ray Society, Larvae of British Butterflies and Moths, vol. i, Plate X, 

 fig. 3 b, 1886. 



2 Nature, vol. xxxviii, 1888, p. 364. 



