74 



SELECTION IN CLADOCERA ON THE BASIS OF 



reaction to light; that the only selection possible in very many cases 

 was from among individuals showing no reaction; and that in the 

 remaining cases the selections in the minus strains were postively 

 reacting individuals with the highest reaction-times. 



Lines 740 and 757 were subjected to selection from August and 

 November 1912 to May 1917. Lines 794, 795, and 796 were used in 

 selection from December 1914 to May 1917. All these lines of S. 

 expinosus, except Line 757, originated from mothers obtained from 

 Pond IV, the larger surface-water pond on the hill, a mile from the 

 laboratory of the Station for Experimental Evolution. 



TABLE 33. Selection summary for Line 794. 



Time period. 



Dec. 23, 1914- 



July 31, 1915 

 Aug. 1, 1915- 



July 31, 1916 

 Test series, 



July 1916... 

 June 1. 1916- 



Aug. 31, 1916 

 Aug. 1, 1916- 



May 1, 1917 



Plus... 

 Minus 

 Plus... 



Minus . 

 Plua... 

 Minus. 

 Plus. .. 

 Minus . 

 Plus... 

 Minus . 



1-27 



1-28 



28-63 



27-61 



62 



61 



59-67 

 69-64 

 64-91 



715.6 

 9.7 



[5.1 



529.4 

 451.8 

 483.8 

 689.1 

 395.9 

 395. S 

 314.4 

 409.6 

 309.9 

 373.* 



334. S 



S24.9 

 266.4 



10.7 



7.1 

 17.2 





 II 



+77.6 



105.S 

 + .7 



15.64.97 



33. 9 S. 80 

 ie'.S4.18 



TABLE 34. Same-day broods. Summary of data for Line 794. 



Time period. 



Deo. 23. 1914- 

 July 31, 1915 



Aug. 1, 1915- 

 July 31, 1916 



Aug. 1, 1916- 

 May 1, 1917 



Plus 



Minus.. 

 Plus. ... 



Plus"! .' .' 

 Minus . . 



7 13.1 

 7 11.6 

 5 16.2 

 13.8 

 2 12.0 

 21S.O 



475 

 S59 

 463 

 4!>0 

 823 



S48.69 



ii 



H 



1 



48 +116 



49.66 2.69 



LINE 794. 



The selection data for Line 794 are given in tables 33 and 34 

 and figure 11. 



This line and Lines 795 and 796 originated from three mothers 

 collected December 11, 1914. Selection was begun with the first 



