742 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



character of series A, or was in the period under discussion. Further 

 evidence as to the effects of selection on fertility, based on series M and 

 N, will be found on page 769. 



Average 

 .Xo. Young 



X 



M 



Generation 1 3 

 Oct 1 . 1903, 



11 lj3 15 



June 1904 



17 19 21 j 23 25 | 28 

 Oct'.'l904 Jan. 1905 Apr. 1905 



Figure 2. Productiveness of fertile pairs in the M and N series. 

 The M and N Series. 



Two other inbred series, M and N (Tables VIII and IX, and Figure 

 2), started by S. O. Mast, showed during the first fourteen inbred gener- 

 ations productiveness much higher than that of series A. The average 

 never fell below 200, except in a single generation of each series, and 



