PHYSICAL CHARACTERS IN MAX -j-j 



and derived normals x normals crive only normal 

 offspring. It is transmitted equally through either 

 sex. In the offspring of crosses between deformed 

 and normals, Lewis and Embleton find a total of 

 forty-four deformed to thirty-two normal. In some, 

 though not all, of the other data of inheritance of split 

 foot, they find a similar excess of deformed individuals, 

 w^hich appears to be significant. It does not neces- 

 sarily follow that the condition is not represented by 

 a single difference in the germ plasm. Indeed, they 

 agree that it has arisen as a " sport " or mutation 

 of germinal origin. They state " there are records of 

 over thirty instances of the origin of this same sport," 

 and account for this by the now widely accepted view 

 that mutations tend to occur and recur in definite 

 directions. Since the character is dominant it cannot 

 remain hidden in the germ plasm, but must appear 

 externally if the germ cell containing it develops into 

 an individual. 



All writers agree that this character segregates 

 sharply, but they claim that it " does not follow the 

 laws of Mendel," because of the excess of abnormals 

 in the offspring of crosses with normals. This does 

 not necessarily follow, for it is now known that many 

 physiological and environmental conditions may cause 

 distortion of Mendelian ratios. Lewis and Embleton 

 beheve there is a " decided tendency for the de- 

 formity to die out " in later generations. They 

 appear to think that this results from the germinal 

 condition representing split-foot becoming unstable. 

 Perhaps the struggle for existence has something to 

 do with it, as well as sexual selection. 



Pearson (1908) refers to the evidence for the 

 existence in Scotland of a family, " the Cleppie Bells," 

 with a deformed hand inheritance extending over 

 two centuries. He traces the deformity in another 

 family for four generations, and finds again an excess 



