PHYSICAL CHARACTERS IN MAX 75 



excess of RH plants (LHr^44-88 per cent.)- This 

 difference may have some connection with the fact 

 that the leaf-blades of barley " are generally slightly 

 twisted into a right-handed screw, while in oats the 

 torsion is in the reverse direction." In maize, again, 

 there is no inheritance of left-handedness or right- 

 handedness as such, but the seeds in odd rows give 

 an excess of RH, those from even rows an equal excess 

 of LH seedlings. The ratios were 54-22 per cent, and 

 46-16 per cent. LH respectively. Thus, the total 

 numbers of LH and RH seedlings from a cob are 

 practically equal. Compton suggests that the 

 differences between row^s in this regard may perhaps 

 be accounted for by unequal pressure on the embryos. 

 In any case it is a relief to find something which is 

 definitely not inherited. The question of the limits 

 of human inheritance will be discussed in a later 

 chapter. 



In 1908 a list of normal and abnormal features 

 in man, whose inheritance had been studied, was 

 published by Hurst, and Bateson (1909) devoted a 

 chapter to this subject. Davenport (191 2) also con- 

 sidered many cases, and Biomeirika contains masses 

 of statistical data on the inheritance of various 

 features. Abnormalities are frequently inherited as 

 dominants, and they probably originated as mutations. 

 Such are hexadactyly, brachydactyly, " lobster claw," 

 some forms of cataract, keratosis, congenital stationary 

 night-blindness (in certain famiUes), and many others. 

 Brittleness of bones or osteopsathyrosis (Conard and 

 Davenport, 191 5) is a remarkable congenital weakness 

 which appears to be inherited as a dominant character. 

 In one recorded case a boy suffered at least twelve 

 fractures of his limbs before reaching the age of three 

 years, being born with both thighs broken. Later 

 this extreme liability to fracture began to diminish, 

 but that it may still remain a serious defect in the 



