chap, xiv.] FREQUENCY OF DIGITAL VARIATION. 401 



dates. On the other hand digital Variation in the Dog seems to 

 be confined to the formation of a hallux in the hind foot, and to 

 duplicity of hallux and pollex \ Similarly though digital Varia- 

 tion is so common in the Pig it is very rare in the Sheep, only 

 one or two clear cases being so far known to me. Note again that 

 polydactylism is common in the Fowl and has been often seen 

 in the Pheasant, while in other birds it is very rare. 



Some one will of course remark that the Fowl is a domesticated 

 bird and the Pheasant is partially so ; but pigeons, ducks - and 

 geese 3 are as much domesticated and in them digital Variation 

 does not seem to be known. The cases in Apes deserve mention 

 in connexion with this matter. One case of syndactylism was 

 quoted in Pithecia No. 525, a case of polydactylism in Macacus No. 

 504?, in Orang No. 511, and in Hylobates No. 508, and a case of 

 ectrodactylism in Macacus No. 526. These five cases surely 

 suggest that Meristic Variation is something more than a mere 

 result of high feeding or of " unnatural " conditions. It is not a 

 little strange that among Apes Meristic Variation should be 

 frequently met with in so many systems of organs. 



(2) Particular forms of digital Variation proper to particular 



animals. 



Of more significance than the frequency with which digital 

 Variation recurs in certain animals is the frequency with which in 

 particular animals it approaches to particular forms, or to particu- 

 lar conditions in a series or progression of forms. This has been 

 seen in the Cat, Man, Horse, Pig, Ox, &c. In each of these the 

 mode of occurrence of Variation has in it something distinctive, 

 something that marks the phenomenon as in some way different 

 from the similar phenomena in other forms. Taking for instance 

 the curious series of cases found in the human manus, ranging 



1 Both these variations are of course very common and may be seen in any 

 walk in the streets. The hallux is very frequently present in the Dachshund and 

 is common in Collies, Mastiffs and other large breeds. In the Mastiff dew-claws 

 (hallux) are not a disqualification (Shaw, Book of the Dog). In the St Bernard the 

 hallux is very often double, perhaps more often than not. This is largely due to 

 the fact that the monks of the Hospice considered the presence of the dew-claw of 

 the utmost importance and preferred it double if possible (Shaw, I.e.). The same 

 writer states that ' the more fully the dew-claws are developed the more the feet are 

 out-turned.' This fact suggests that there may be a change of Symmetry like that 

 in the Cat, but I have no observations on the point. I have several times seen 

 simultaneous duplicity of hallux and of pollex in the same individual (Dachshund, 

 &c). Other digital variations must be rare in dogs as there are hardly any recorded 

 cases. A problematical case of ectrodactylism is given by Baum, Deut. Ztochr. f. 

 TJiierm., xv. 1889, p. 709, Jig. [q. v.]. I once saw a mongrel Fox-terrier with no 

 pollex on either manus, but I was not satisfied that they had not been cut off, 

 though there was no suggestion of this. 



- For an interesting account of a Duck with the webs of the toes almost wholly 

 absent see Mobius, Zool. Gart., xvm. 1877, p. 223. Another case of the same kind 

 Morris, F. 0., Zool., iv. p. 1214. 



3 Pygomelian geese often recorded; e.g. Clelaxd, Proe. Phil. Soc. Glasg., 

 xvm. 1886, p. 193,^.; Wyman, Proc. Bost/N. H. S., vm. 1861, p. 256. 



b. 26 



