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- Ave see that 

 their variations bear no definite relation to those of the body, 

 and not much to those of each other. With 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 A'ery gieat, 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 Avhich happen to be in a particular museum. 



To prove that this is not an isolated case, Professor Milne 

 Edwards also gives a table shoAving the amount of variation in 

 the museum specimens of six common species of lizards, also 

 taking the head as the standard, so that the comparative 

 variation of each part to the head is giA^en. In the accompany- 

 ing diagi^am (Fig. 2) the A-ariations are exhibited by means of 

 lines of A^arying length. It Avill be understood that, hoAvever 

 much the specimens A'aried in size, if they had kept the same 

 proimiions, the variation line Avould haA-e been in every case 

 reduced to a point, as in the neck of L. velox aa hich exhibits 

 no A^ariation. The diiTerent proportions of the Aariation 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 AA'hateA'er amount of variation occurs 

 among a fcAv specimens aaiII 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 Avith the actual 

 length of the head (given beloAv the diagram) which Avas used 

 as a standard in determining the variation, but AA^hich itself 

 seems not to have A-aried.^ 



Variation among Birds. 



Coming noAv to the class of Birds, Ave find much more 

 copious evidence of A^ariation. 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- 

 ^ Ann, des Set. Nat., torn. xvi. p, 50. 

 E 



