78 



SELECTION IN CLADOCERA ON THE BASIS OF 



Casual examination seems to reveal at once the fact that there 

 is no effect of selection, and this is probably correct, but on careful 

 analysis it is not altogether certain that an effect of selection is 

 entirely lacking. The plus strain is generally the less reactive, but 

 the curve for the minus strain is extremely fluctuating. 



For the first longer period (8 months) the mean for the plus 

 strain was 703.3 seconds, for the minus strain 571.4 seconds (table 



TABLE 35. Selection summary for Line 795. 



Time period. 



Dec. 24, 1914- 



July 31, 1915 

 Aug. 1, 1915- 



July 31, 1916 

 Test series, 



June 1916... 

 May 1, 1916- 



July 31, 1916 

 Aug. 1, 1916- 



May 1, 1917 



Strain. 



Plus.. 



Minus 

 Plus. . 

 Minus 

 Plus.. 

 Minus 

 Plus.. 

 Minus 

 Plus. . 

 Minus 



1-27 



1-27 



28-65 



28-64 



60 



60 



57-65 

 56-64 

 66-94 

 65-96 



24 



10. 

 2263. 



S 60. 8 1338 



16. 



1 



8 10.3 

 8 



4 



14. 



20 14. 



3 

 " 



"H 



292 

 .? 

 580 

 376 

 1397 



129 



356 



2S7 



2 



i! 



164 

 103 

 301 



733 



683 



60 



115 



02 



425 

 317 

 325 



230 

 188 

 181 



133 



900 

 875 

 842 

 70S 

 880 

 SS3 

 750 

 776 

 815 

 735 



703.3 

 671.4 

 625.0 

 530.7 

 615.4 

 591.6 

 594.7 

 44S.1 

 457.2 

 502.0 



254.4 



500. i 



308.5 

 323.1 

 330.9 

 366.1 

 316.7 

 341.7 

 326.4 

 330.1 



10.0 



12.1 



8.6 



11. 



6.0 



6.6 



18.8 



25.5 



11.7 



II 



+ 131.9 

 '+94 '.3 



+23.8 



+ 146.6 

 "-44.8 



15.7 



8.40 



14.26.64 

 ' 8!9 2. 67 



31.64.63 



17.62.66 



TABLE 36. Same-day broods. Summary of data for Line 795. 



Time period. 



Dec. 24, 1914- 

 July 31, 1915 



Aug. 1, 1915- 

 July 31. 1916 



Aug. 1, 1916- 

 May 1, 1917 



Strain. 



Plus... 

 Minus . 

 Plus... 

 Minus . 

 Phis... 

 Minua . 



1210. 



12.6 



6 14- 



139 



162 



1*3 



63 



73 



"8 



363 

 354 

 334 

 278 

 117 



900 

 S7S 

 725 

 818 

 714 

 000 



661 

 50S 

 617 

 470 

 307 

 671 



i 



277.77 

 299.17 

 323.84 

 337.18 

 263.21 

 SIS. 97 





15.89 

 17. S4 

 17.16 

 20.51 

 22.37 

 4.78 



1| 



cl 



4J 



IS 

 1.2 



S a 



I -a 



+63 



+'i38' 



23.89 

 26! 74 



S3.3S 



2.63 



35). The difference was +131. 9 15. 7 seconds, or 8.4 times the 

 probable error. The 12 same-day broods for this period likewise gave 

 a mean for the plus strain in excess of the minus strain (table 36). 

 The difference was -f63 23.89 seconds, 2. 63 times the probable error. 

 For the second longer period (August 1915 July 1916) of the 

 data for this line the means were 625.0 and 530.7 seconds for the 

 plus and minus strains. The difference was 4- 94. 3 14. 2 seconds. 

 This difference was 6.64 times the probable error. Twelve same- 



