344 MEMSTIC VARIATION. [part i. 



ternal condyle is thus much larger than that of the normal femur, but 

 there is in it only a very slight suggestion of a division into two parts. 

 The innominate bone has an ilium which anteriorly is normal, but 

 which posteriorly enlarges and to some extent divides into two parts, i 1 

 and i 2 . Of these the ventral part, i\ unites with a nearly normal pubis, 

 p, and bounds the shallow acetabulum with which the femur articu- 

 lates. The rest of this acetabulum is made up by the ischium, is 1 , of 

 the "anterior" limb, which together with the pubis bounds an obturator 

 foramen, of 1 . Dorsal to these parts the ilium has a partly separated 

 portion, i 2 , which forms part of the wall of a cavity apparently repre- 

 senting the acetabulum of the "posterior" limb. Dorsal to this a 

 complete ischium arises which bears a normal ischial tuberosity and 

 curves round a second smaller obturator foi'amen, of 2 . 



In so far as the foregoing description involves conceptions of 

 homology it is merely suggestive, but the structure of the innomi- 

 nate bone leaves little doubt that the nature of the parts is much as 

 here described. Nevertheless the appearance of the digits 5 and 6 

 and of the tarsal bones c 3 to c 6 somewhat suggests that there is a 

 symmetry about an axis passing between the digits 5 and 6 ; but 

 if 5 were a minimus and if 6 were fashioned as an index, which it 

 is, the appearance of a relation of images would to some extent 

 exist in any case. This appearance is however confined to the 

 dorsal aspect of the foot and is not present on the plantar aspect. 



This case, if the view of it proposed be true, differs from other 

 examples of double-hand (e.g. Nos. 491 to 499) in that the Repe- 

 tition is Successive and is not a Repetition of images ; for the 

 digits stand I, II, III, IV, V, II, III, IV, V, and not V, IV, III, II, 

 [I], II, III, IV, V as in those other cases. In this respect it is so 

 far as I know unique. 



Those who have treated the subject of double-hand generally make reference 

 to the following records. Rueff, De conceptu, Frankfurt, 1587, PI. 41 ; Aldro- 

 vandi, Blonstr. Hist., 1642, p. 495; Kerckring, Obs. anat., Arnst. 1670, Obs. xx. 

 PL, but the descriptions are scarcely such as to be useful for our purpose. A case 

 quoted by Dwight, Mem. Bost. Soc.of N. H., iv. No. x. p. 474, from du Cauroi, Jour, 

 des Scavans, 1696, pub. 1697, p. 81 [originally quoted by Morand and misquoted by 

 many subsequent authors], is probably not an example of double-hand (see No. 522). 



Cases of Polydactylism in Man and Apes not associated with 

 definite change of Symmetry. 



From the evidence as to polydactylism in general the foregoing 

 cases have been taken out and placed in association as exhibiting 

 the development of a new system of Symmetry in the limb. It 

 will have been noticed that in all of them the external (ulnar or 

 fibular) parts of the limb remain unchanged, and the parts not 

 represented in the normal are on the internal (radial or tibial) 

 sides. In the remaining cases of polydactylism, which constitute 

 the great majority, there is no manifest change in the general 

 symmetry of the limb. 



