46 
DARWINISM 
CHAP. 
wings, on which generic and family distinctions are often 
established, are also subject to variation. The Rev. R. P. 
Murray, in 1872, laid before the Entomological Society 
examples of such variation in six species of butterflies, and 
other cases have been since described. The larvae of butter¬ 
flies and moths are also very variable, and one observer 
recorded in the Proceedings of the Entomological Society for 
1870 no less than sixteen varieties of the caterpillar of the 
bedstraw liawk-moth (Deilephela galii). 
Variation among Lizards. 
Passing on from the lower animals to the vertebrata, we 
find more abundant and more definite evidence as to the 
extent and amount of individual variation. I will first give a 
case among the Reptilia from some of Mr. Darwin’s un¬ 
published MSS., which have been kindly lent me by Mr. 
Francis Darwin. 
“ M. Milne Edwards ( Annates des Sci. Nat., 1 ser., tom. 
xvi. p. 50) has given a curious table of measurements of four¬ 
teen specimens of Lacerta muralis; and, taking the length of 
the head as a standard, he finds the neck, trunk, tail, front 
and hind legs, colour, and femoral pores, all varying wonder¬ 
fully ; and so it is more or less with other species. So ap¬ 
parently trifling a character as the scales on the head affording 
almost the oidy constant characters.” 
As the table of measurements above referred to would give 
no clear conception of the nature and amount of the variation 
without a laborious study and comparison of the figures, I 
have endeavoured to find a method of presenting the facts to 
the eye, so that they may be easily grasped and appreciated. 
In the diagram opposite, the comparative variations of the 
different organs of this species are given by means of variously 
bent lines. The head is represented by a straight line because 
it presented (apparently) no variation. The body is next 
given, the specimens being arranged in the order of their size 
from No. 1, the smallest, to No. 14, the largest, the actual 
lengths being laid down from a base line at a suitable 
distance below, in this case two inches below the centre, the 
mean length of the body of the fourteen specimens being two 
inches. The respective lengths of the neck, legs, and toe of 
