Ill 
VARIABILITY OF SPECIES IN A STATE OF NATURE 49 
each specimen are then laid down in the same manner at 
convenient distances apart for comparison; and we sec that 
their variations bear no definite relation to those of the body, 
and not much to those of each other. AYith the exception of 
No. 5, in which all the parts agree in being large, there is a 
marked independence of each part, shown by the lines often 
curving in opposite directions; which proves that in those 
specimens one part is large while the other is small. The 
actual amount of the variation is very great, ranging from 
one-sixth of the mean length in the neck to considerably more 
than a fourth in the hind leg, and this among only fourteen 
examples which happen to be in a particular museum. 
To prove that this is not an isolated case, Professor Milne 
Edwards also gives a table showing the amount of variation in 
the museum specimens of six common species of lizards, also 
hiking the head as the standard, so that the comparative 
variation of each part to the head is given. In the accompany¬ 
ing diagram (Fig. 2) the variations are exhibited by means of 
lines of varying length. It will be understood that, however 
much the specimens varied in size , if they had kept the same 
proportions, the variation line would have been in every case 
reduced to a point, as in the neck of L. velox which exhibits 
no variation. The different proportions of the variation lines 
for each species may show a distinct mode of variation, or may 
be merely due to the small and differing number of specimens ; 
for it is certain that whatever amount of variation occurs 
among a few specimens will be greatly increased when a much 
larger number of specimens are examined. That the amount of 
variation is large, may be seen by comparing it with the actual 
length of the head (given below the diagram) which was used 
as a standard in determining the variation, but which itself 
seems not to have varied. 1 
Variation among Birds. 
Coming now to the class of Birds, we find much more 
copious evidence of variation. This is due partly to the fact 
that Ornithology has perhaps a larger body of devotees than 
any other branch of natural history (except entomology); to 
the moderate size of the majority of birds ; and to the circum- 
1 Ann. des Sci. Nat., tom. xvi. p. 50. 
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