6 4 



VARIATION 



Other and similar cases are given, though the latter is the 

 only one described in which the syndactylism is complete in all 

 four feet. It is, however, generally simultaneous in fore and 

 hind feet. 1 



Absence of parts in a linear series. Men with hands but no 

 arms, with feet but no legs, are not unknown. Whether the 

 missing parts are really dropped out of the series, or whether 



they were originally present but 

 suffered abortion during embry- 

 onic development, being repre- 

 sented at maturity by rudimentary 

 parts, is uncertain, though zoolo- 

 gists would incline strongly to the 

 latter view. The exact fact would 

 have an important bearing upon 

 the unit of variability, the nature 

 of heredity, and the manner of 

 differentiation. 



Whatever the fact in this re- 

 gard, variations of this order are 

 manifestly rare as compared with 

 the increase or decrease in strictly 

 multiple parts. In other words, 

 while considerable deviation in the 

 num ber of similar members (as 



. . . \' 



fingers) is common, it is exceed- 

 ingly uncommon for an entire 



group (as the hand) to be omitted, rarely from the end of 

 the series (as the foot or hand) and still more rarely, if ever, 

 from the middle of the series, as would be the case in a truly 

 missing arm (humerus, radius, and ulna), but with the hand 

 present, coming directly from the body. 



Extra legs. The repetition of a member as complicated as a 

 leg is extremely unusual but by no means unknown. The writer 



1 Bateson gives many similar cases, each with some peculiarity of its own. 

 Solid-hoofed pigs are seen so frequently and at points so widely removed both 

 in time and space (mentioned by Aristotle and reported from many regions of the 

 earth) (see Bateson, Materials, etc., p. 387) that this would seem to be a variation 

 that has often arisen afresh. 



FIG. 16. Meristic repetition in leg: 



. right leg of beetle repeated in 



triplicate. - After Bateson 



