THE SELECTION PROBLEM IN ANIMAL BREEDING 497 
TaBLe LXIV.—Tue Tren Greatest Propucers or SPEED UP TO AND INCLUDING 1901 
(After E. Davenport) 
eee 
Pacers Total 
Sires | Sired by | Trotters 
Nutwood 600............... | Belmont 64 | 131 34 165 
Electioneer 125.............. Hambletonian 10 | 158 2 160 
Onward 1411................) Geo. Wilkes 519 124 | 34 158 
Red Wilkes 1749............ | Geo. Wilkes 519 116 | 41 157 
Alcantara 729............... Geo. Wilkes 519 102 47 149 
Pilot Medium 1579.......... Happy Medium 400 | 94 20 114 
Simmons 2744...............| Geo. Wilkes 519 82 23 105 
Wilton 5982.................| Geo. Wilkes 519 89 14 103 
Gambetta Wilkes 4651....... Geo. Wilkes 519 | 49 52 101 
Baron Wilkes 4758...........| Geo. Wilkes 519 | 78 21 99 
a few generations, therefore, this famous family of racing horses has 
produced a remarkable series of performers, horses which have been 
able to trot or pace a mile within 2:30. There seems to be little question, 
therefore, that this family of fast horses had its foundation in the care- 
ful fostering of the favorable genotypic material of Hambletonian 10; 
and a transmission of it through a relatively small number of exceptional 
sires which may have possessed a genotypic arrangement somewhat 
superior to that of Hambletonian 10, as the record of Geo. Wilkes 519 
in particular might indicate. Davenport has made a very careful study 
of the records in the Register and Yearbook, a study which should be 
continued and extended. Without considering in any detail the ex- 
tensive data which have been collected, it appears fairly certain that 
selection in the improvement of trotting and pacing horses has operated 
by detecting and multiplying the most favorable genotypes; and that 
training, in so far asit has had influence, has served as a means of developing 
inborn potentialities to the full, and, therefore, of detecting most favorable 
lines of descent. 
Fecundity in Fowls.—Pearl’s investigations on the inheritance 
of fecundity in fowls have already been touched upon, but they deserve 
more extended treatment at this point, for in them the relative effective- 
ness of phenotypic and genotypic selection is strikingly contrasted. 
For if performance has anything to do with development of more favorable 
hereditary material, or if selection has a creative effect in a given direc- 
tion, then it would appear to be a conclusion unavoidable that mass 
selection must result in increased average winter egg production. Yet 
as a matter of fact, as shown graphically in Fig. 185 there was actually 
a slight decrease in average winter egg production during a 9-year period 
of such selection. 
That this selection was rigid and a fair demonstration of the ineffect- 
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