502 TRANSMISSION 



rather than with individuals, and with large fraternities rather than with 

 small ones. We ought, for example, to compare the group containing both 

 parents and all the uncles and aunts with that containing all the children. 



Here is the very gist of the whole matter, showing the folly 

 of dealing with individuals in questions of breeding. All the best 

 evidence shows that selection based upon the individual, without 

 regard to the group to which he belongs, will never result in 

 concentration of excellence. It is only by persistent selection, 

 based on the groups as a whole (purity of pedigree in the sense 

 of uniformity of type), that we shall ever free even the family 

 from the drag of the race, and make real progress in improvement. 



Harold and Miss Russel, the sire and dam of Maud S., were 

 owned at Woodburn for many years, but of all their get only one, 

 Maud S., developed high speed. Why ? The question cannot be 

 answered any further than it can be inferred from the principle 

 just stated and from the well-known methods of cleavage of the 

 nucleus in cell division and in maturation ; but with these facts 

 in mind, we should hardly expect that two identical individuals 

 would ever arise, even from the same parents. 



The earlier offspring live longer than do the younger children 

 of the same parents. Having established the fact that successive 

 offspring of the same parents are different, there remains the 

 task of determining to what extent this fraternal variability is 

 heterogeneous, and to what extent it may be correlated with age 

 or with some similar circumstance that tends to throw the off- 

 spring into a regularly graded series of some sort. 



On this point we know but little. To the eye this variability 

 appears quite heterogeneous, but studies in longevity, for ex- 

 ample, have fully established the fact that in man the older chil- 

 dren, on the average, live longer that is, have longer lives 

 than do the younger ones of the same family. This difference, 

 as between the oldest and the youngest, amounts to no less than 

 four years. 1 Whether the same or a similar decline takes place 

 in other characters and faculties only exhaustive studies could 

 determine. There is no reason to doubt that general principles 

 apply equally to man and to other animals, excepting in so far 



1 See article on " Inheritance of the Duration of Life," by Beeton and Pearson, 

 Bioinetrika, Vol. I, Part I, pp. 50-76. 



