DESCENT WITH MODIFICATION 163 



The exceptional offspring and his parent. A glance at the table 

 on page 156 will show another great principle in transmission, 

 namely, that a given class of offspring may be produced in vari- 

 ous ways. For example, the heights of offspring as recorded in 

 column 1 3 are clearly exceptional. These people are over six feet 

 tall, but they were produced by all sorts of parents from 72.5 inches 

 dozvn to 65.5. While the parents were thus distributed, yet the 

 greatest number of exceptional people (11) came from mediocre 

 parentage, but the greatest proportion of tall people came from 

 extremely tall parentage. Thus the 1 1 of this column were the 

 product of 183 families (see column 16); while as many as 7 

 were produced by 19 midparents that were three inches taller, 

 — another evidence of regression and of progression as well. 



Reversion. When we see how many tall people beget short 

 children and how many tall children come of short parents (see 

 rows h and k in the table), we are not surprised that occasion- 

 ally an unaccountable case will turn up, as when a red-headed 

 boy is born of black-haired parents, and nobody can remember 

 even a red-headed grandparent. Aye, remember ; there 's the 

 trouble.. The total ancestry runs back for many generations and 

 we remember but a few, — rarely back of the grandparent, — 

 whereas each of us has over two thousand ancestors within ten 

 generations. In the case of the red-headed boy some one of them 

 was in all likelihood red-headed, and this that has turned up is 

 a " reversion " to that ancestor ; for every individual transmits 

 all the characters of his ancestry, and anything that is trans- 

 mitted may at any time become dominant and then visible. 

 That is about all there is of the matter of reversion or throw- 

 ing back, about which such a "to do" has been made. As a 

 physiological fact it is interesting; as a matter in plant or 

 animal improvement it hardly applies, for as soon as systematic 

 selection is a little while practiced, the chance of reversion 

 rapidly reduces to practically nothing. 



Degeneracy. This is a matter of importance in human affairs 

 rather than in those of the animal and plant, but facts such as 



