734 



THE AMEBIC AN NATURALIST 



[Vol. XLV 



parental types by breeding back to the desired type— the 

 1 1 pure sire" method — than to extract it from F 2 hybrids 

 by the operation of the laws of chance. In the general 

 run of cattle the 7 /8 grades are quite like the pure types ; 

 15/16 grades are much more so, while 31/32 or 63/64 are 

 generally so like the pure breed as to be, except for 

 arbitrary rules, eligible for registration. All of which 

 tends to support the pure gamete theory, in that under 

 such a process the laws of chance rapidly " quarter out" 

 the foreign units, albeit rigid selection can, of course, as 

 it often does, maintain any one of the mongrel types indef- 

 initely. If the number be great, the longer the process 

 and the more likelihood of "reversion." The theory of 

 the pure gamete is not inconsistent with the somatic blend 

 in F 1 ; in fact, it demands it in the coarser aspects. Such 

 a blend indicates that a unit complex rather than a single 

 unit is under observation. 



All the data so admirably collected by Barrington and 

 Pearson yield most readily to a Mendelian interpretation, 

 if by such interpretation is meant the purity, segregation 

 and fortuitous recombination of the unaltered deter- 

 miners of unit characters, provided such interpretation 

 is not held to be inconsistent with frequent intra-zygotic 

 reactions between the determiner and some antibody 

 occasioned by the definite relative concentration and 

 intimacy of the two bodies. They reject a Mendelian 

 interpretation on the grounds that the whole coat does 

 not behave as a single unit. Gametic purity of the unit 

 character might as well be rejected on the grounds that 

 the whole animal with its thousands of characters does 

 not so behave, or that there are occasional intra-zygotic 

 reactions causing mutations. In mentioning the types of 

 cattle going into the making of the Shorthorn, they con- 

 tinue : 



Upon the ingredients just referred to, the breeders had to work when 

 pedigree cattle breeding, which is scarcely more than a century old, 

 came into vogue. The Shorthorn had possibly arisen from four races : 

 the Celtic, a Romano-British, an Anglo-Saxon and the "Dutch" and 

 even some of these are mixtures. . . . Thus the Shorthorn Red may 



