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THE AMERICAN NATURALIST [Vol. XLVIII 



3 rhomboidea (1 BBnn, 2 Bbnn), 



1 simplex (bbnn). 

 Since BbNn, BBNn and bbNn, in the earlier experi- 

 ments, might have been confounded in the later stages, 

 and since there is little doubt as to the earlier stages, 

 these three forms have been combined in Table V. 



table v 



Eesults from Selected Setchelliana (BbNn) 



This, especially in the case of No. 3,613, is a fairly close 

 approximation to what we might expect. When in No. 

 3,613 we attempt to distinguish between Setchelliana, 

 Treleaseana and attenuata, we get the following num- 

 bers, the expected numbers following in parentheses: 

 BbNn 39(45), BBNn 21(22.50), bbNn 34(22.50), the last 

 number being far too high. When the experiments were 

 begun, we distinguished only between "narrow," 

 ' 1 broad ' ' and ' ' linear. ' ' To-day we know that the ' ' nar- 

 rows" include Treleaseana, Setchelliana and attenuata, 

 that the "broads" include rhomboidea and simplex, while 

 the linears are identical with arachnoidea. In this light 

 it is of interest to go back to the first generation of 1910. 

 Our data yield the figures given in Table VI. 



