122 On Heterochromia Tridis in Man and Animals 



straight hair pattern occurred. The curly tufted negro hair covered 

 the sides of the scalp while the straighter hair formed a patch on the 

 vertex in each case. (Plate IX, fig. 1.) 



In these two children genetic factors which normally control the 

 epistatic negroid type of hair structure over the whole scalp behaved 

 differently in different scalp areas, and the true explanation of irregular 

 or ray iris pattern and oi harlequin coat colour pattern will probably 

 apply to this abnormality in hair structure pattern also. 



PART II. 



Irregular Eye Colour Pattern and the Constitution of 

 Gametic Factors. 



Irregular iris pigmentation of the ray type and indivisibility of 

 gametic factors in heredity. 



It has been customary to regard gametic factors as indivisible units 

 like the chemist's atom. 



Thus Punnett(lO) {Mendelism, p. 39) says, " Unit characters (in the 

 zygote) are represented by factors in the gametes which behave in the 

 process of heredity as indivisible entities." 



Now if in the " B" human family we regard the male parent G. B. as 

 a heterozygous duplex of irregular or ray pattern, then, according to 

 expectation, the mating of this individual with a simplex recessive 

 should result in equal number of simplex and duplex offspring in the 

 Fi generation, whereas the actual numbers are seven simplex and three 

 duplex of which two are of the irregular ray pattern like the father in 

 a family of ten. 



But a further difficulty arises with the manner of transmission of 

 the irregular or ray pattern itself. 



For although two of the three duplex children are partial or ray 

 duplex like the father, the distribution of the irregular pattern is not 

 the .same in the parent and the children. 



The pigmented ray appears in the right eye instead of the left (as 

 in the father) in one child, and in the opposite half of the same iris in 

 the other child. 



How can we explain this different incidence of pattern in the passage 

 from father to children ? 



Either the complication arises in some alteration in the composition 

 or arrangement of the duplex factors in the gametes of the male parent, 



