248 PLANT HYBRIDIZATION BEFORE MENDEL 



"The law of regression tells heavily against the full hereditary trans- 

 mission of any gift. Only a few out of many children would be likely 

 to differ from mediocrity so widely as their mid-parent, and still fewer 

 would differ as widely as the more exceptional of the two parents. . . ." 

 (p. 106.) 



"It must be clearly understood that there is nothing in these statements 

 to invalidate the general doctrine that the children of a gifted pair are 

 much more likely to be gifted than the children of a mediocre pair. 

 They merely express the fact that the ablest of all the children of a few 

 gifted pairs is not likely to be as gifted as the ablest of all the children 

 of a very great many mediocre pairs." (p. 106.) 



From the data obtained, Galton undertook to calculate the value 

 of the respective contributions of the successively ascending an- 

 cestors to the inheritance. 



"if D is the stature of the mid-parent, then mid-parents whose stature 

 is P D have children whose average stature is P 2/3 D. In other words, 

 a character in a man implies a character of 1/3 of that amount in his 

 mid-parent. Likewise the character in the mid-parent of the man being D, 

 the same character in the mid-parent of the mid-parent would be 1/3 D, 

 that of the mid-great-grandparents 1/9 D, and so on. Hence the total 

 inheritance would be represented by D (i + i/3+l/9+&c.)=D 3/2." 



(P- 134-) 



By theoretical calculations (p. 13^) Galton arrives, from two 

 different directions, at the figures 4/9 and 6/11, respectively, as 

 representative values for the extent to which the mid-parents' 

 characters are represented in, or, as he says, "influence" the off- 

 spring. These values, 44/99 and 54/99, as he says, "differ but 

 slightly from 1/2, so we may fairly accept that as the result." 



"Hence the influence, pure and simple, of the mid-parent may be 

 taken as 1/2, and that of the mid-grandparent as 1/4, and of the individ- 

 ual grandparent 1/16, and so on. It would, however, be hazardous, on the 

 present basis, to extend this sequence with confidence to more distant 

 generations." (p. 136.) 



With respect to the inheritance of eye-color, Galton makes com- 

 ment as follows : 



"stature and eye-colour are not only different as qualities, but they are 

 more contrasted in hereditary behaviour than perhaps any other common 

 qualities. Parents of different statures usually transmit a blended inheri- 

 tance to their children, but parents of different eye-colours usually trans- 

 mit an alternative heritage, if one parent is as much taller than the 

 average of his or her sex as the other parent is shorter, the stature of 

 their children will be distributed, as we have already seen, in nearly 

 the same way as if the parents had both been of medium height. But if 

 one parent has a light eye-colour, and the other a dark eye-colour, some 

 of the children will, as a rule, be light and the rest dark; they will 



