MERISTIC VARIATION 



which the middle one was almost bilaterally symmetrical, while the hoofs 

 of the other two turned toward it." 1 



Bateson says of the pig that he knows of no case of polydac- 

 tylism in the hind feet. All cases described are of the fore feet, 

 and the extra toes are on the internal side 

 of the digital series. 



Syndactylism in cattle, sheep, and pigs. 

 By this term is meant a real union of 

 digits ii and in into a single bone incased 

 in a single hoof, as in the solid-hoofed hogs. 



According to Rosenberg, as quoted by 

 Bateson, 2 in the normal sheep " the meta- 

 carpals n and v are distinct in the 

 embryonic state, afterwards completely 

 uniting (fusing) with in and iv." 3 This 

 throws some light upon the whole ques- 

 tion, as tending to explain not only certain 

 cases of polydactylism but all cases of 

 syndactylism. 4 Again quoting Bateson : 



FIG. 1 5. Said to be the right 



1. A young ox having the two digits of the forefoot of cow: digits in 

 right fore foot completely united. 



2. Calf: each foot having only one hoof, 

 though all the bones were normal. 



3. Same as above, except that in the fore foot the normal digits (in and 

 iv) were completely united, bearing a single hoof. The same condition 

 was found behind, except that the hoof was more pointed. 



4. A fore foot and a hind foot of the same individual (pig), in which 

 the two chief digits were completely united, viz. represented by a single 

 series of bones. 



possess a greater number of digits, it is habitual with many to regard it as a case 

 of atavism, the reappearance of a long-lost character. But how is it in the case 

 of man when a sixth or even seventh digit appears ? This must be meristic varia- 

 tion and not atavism, because no six-toed species of any sort has ever been 

 described or its existence suspected. Meristic variation, therefore, is not limited 

 to lost characters or to numbers once normal, but may go far in excess of either. 

 Here, then, is need for discrimination, for even the appearance of a character that 

 has been once lost is not absolute evidence of atavism. 

 1 Bateson, Materials, etc. p. 381. 2 Ibid. p. 383. 



3 The former from failing ever to unite, the latter from a continuation of the 

 fusing process to include in and iv. 



4 That is, ii unites with in, and v unites with iv during development. 



two groups of two each. 

 After Bateson (from 

 Delplanque) 



