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Show 48 Lacerta oce/la ta Lacerta uiridis Lacerta agilis Lacerta muralis Lacerta uelox Lacerta deserti DAH.WINISM CIIAI'. 1=11 -- -------------------- ________ Neck .... ___________________ Body ~- ________________ Hind Legs ---------.Tail _____________________________ NBoecdky •_-· -_--_--_--_--__ _HTainild Legs _ ____ Neck ._ __ _____ Body _ ________ __)find Legs ._ _______________________ .Neck _.. Body _____ .JJHind Legs •-----------t Tail , _______ Neck ,_ _ _, __ Body .... _____ _Hind Legs · ----------- Tai I • ---------- _______________ Neck .._ ___________ Body ,_..________________ __Hind Legs -----------•Tail Length of Head taken as tho stanaard in each of the aboue-named specieJ Fro. 2. - Variation of Lizanls. m VARIABITXl'Y OF SPECIES IN A STATE OF NATURE 49 each specimen arc then h.tid down in the sn.mc manner at convenient distances apart for comparison ; and we sec that their variations bear no definite rela,tion to those of tho body, and not much to those of each oth r. With the cxceptim1 of No. 5, in which all tho parts agree in hcing large, there i. a marked independence of each part, shown by the lines often curving in oppo. ito directions; which proves that in those specimens one part is large while the other is small. 'l'hc actual amount of tho variation is very great, ra,nging from one-sixth of the mean length in the neck to considerably more t hn.n a fourth in the hind leg, and this nmoncr only fourteen examples which happen to be in a pm'ticnlar museum. To prove that this is 11ot an isolated case, Professor Milne Edwards also gives a tnlJlc showing the amount of variation in the museum specimens of six common species of lizards, al. o taking the head a. the standard, so that the comparative variation of each part to the head is given. In the accompanying diagram (Fig. 2) the variations arc exhibited by means of lines of varying length. It will he nndcrstood tl1at, however much the ~pccimcns varied in size, if they had kept the Ramo proportions, the variation line would have been in every caRe reduced to a point, as in the neck of L. vclox which exhibits no variation. The different proportions of the variation lin . for each species may show a distinct mode of variation, or may be merely due to the small and diffcrincr number of specimens; for it is certain that whatever amount of variation occurs among a few specimens will be greatly incrcascfl 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 diacrram) which was used as a standard in determining the variation, but which itself seems not to ha vc varicd.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 fa<.:t 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; aml to the circum - 1 Ann. des Sci. Nat., tom. xvi. p. GO. :E |