(23) 



obtained with much fewer selections. This is true, of 

 course, because the average character of the progeny of 

 an individual gives a much more accurate test of its hei'- 

 editary constitution than does its external appearance. 



If this is true in a population, may it not also be 

 true within a clone % And if one seeks for an effect of 

 selection within a clone, v;hy not use the type of selection 

 which has been found to be most effective in populations ? 



Selection experiment 3. Quick effect of individual 

 selection based on progeny. In accordance with the 

 train of reasoning set forth above, in my next experiment 

 individual selection, based on the average spine number 

 of the progeny, was usdd. On October 10, 1915, an indi- 

 vidual was isolated from the Homewood pond. After it had 

 produced five progeny it was discarded, Eacl: of these 

 progeny, in turn, produced five offspring and wan then 

 discarded. Of these five sets of offspring, the set with 

 the highest average spine num.ber and the set with the lov/- 

 est v/ere allowed to produce five progeny each. The other 

 three sets were discarded. Then another selection was 

 made, the set of progeny with the highest average spine 

 number being retained on the high side, and vice versa on 

 the low side. This method of selection was continued for 

 another generation. 



Table VII shows the pedigree of this experiment. In 

 this table, 5a, 5b and 5c are the progeny of individual 5; 

 5al, 5a3, 5a4 and 5a5 are the progeny of 5a; and so on. 

 The numbers in parentheses, following the numbers which 



