VARIATION IN EUROPEAN LEPIDOPTERA. 



79 



luxuriant foliage, and at the same time that of stunted and im- 

 poverished growth. 



We now come to the consideration of those two controlling laws 

 which affect all natural organisations, whether vegetable or animal — 

 namely, those which control the transmittal of parental forms and 

 characteristics to their offspring. The first of these natural laws is 

 that of inheritance or persistence, and this is so all-powerful in some 

 species that we find their individuals identical in every part of the 

 world to which they have spread. Vanessa Antiopa and Lithosia 

 pulchella are, I believe, cases in point. 



But there is a second natural law which acts apparently in 

 antagonism to the former, and its operation is to effect some slight 

 alteration in each individual. And sometimes we find a large portion 

 of a group affected by a common tendency to vary in a similar 

 direction ; and this seems to point frequently only to a secondary 

 phase of operation of the first law, inasmuch as most of such cases 

 are merely evidences of a tendency to revert to some ancestral 

 pccuharity which had become effete. The Lycaenidse have in more 

 than one species a tendency for two or more spots on the under 

 surface of the fore wing to coalesce, and form a band or streak- 

 Several species and varieties of Polyommatus have the characteristic 

 copper colour shot with violet, which tendency has developed itself 

 permanently in P. Alcipli7vn, etc. Among the Zygaiiidce we find the 

 crimson varied by yellow, and of this we have extreme examples in 

 some local English aberrations of Z. Filipendulce^ and Z. Trifolii^ in 

 which the red is wholly supplanted by yellow. Several continental 

 species, Z. Fausta and Z Carniolica, etc., have the crimson spots 

 encircled more or less deeply by yellow. Again, the purple which 

 tinges the under surface of the hind wing of several species of 

 Argyiinis, varies in intensity occasionally, and it runs in different 

 degrees of strength through several species. Arg. Amathiisia shows 

 the character in its fullest development, while it shades down through 

 A. Dia (Weaver's fritillary), A. Ino^ and A. Paphia into a mere trace, 

 while A. Pandora, a species nearly related to A. Paphia, has lost this 

 trait altogether. A remarkable aberration of A. Paphia was taken a 

 few years since at Pembroke, by Mr. Barrett, with the under surface 

 of the hind wing completely shot with purple, thus illustrating what 

 may be called a generic aberrant tendency. Darwin formulates these 

 phenomena thus : — 'Distinct species present analogous variations, and 

 a variety of one species often assumes some of the characters of an 

 allied species, or reverts to some of the characters of an early 

 progenitor.' 



Aberrations once having occurred, the law of heredity steps 



Nov. 1884. 



