1^0. 645] 



VEBTEBBJE OF FISHES 



369 



Lepomis incisor, therefore, a higher number of segments 

 was developed in the year class developed at the lower 

 temperature. The detailed data are given in Frequency 

 Tables II and III. 



Evidence has already been given indicating that the 

 1919 year-class of Notropis atherinoides is divisible into 

 three subclasses, of which the middle (B) developed dur- 

 ing colder weather than either the first (A) or the last 

 (C ) . The data given in Frequency Table IV and in figure 

 6 demonstrate that this subclass B possesses a decidedly 

 higher number of vertebrae than either of the other two. 

 The averages are as follows : for the 146 specimens of sub- 

 class A, 41.38 (+0.04) ; for the 845 comprising subclass 

 B, 41.84 ( + 0.02) ; for the 97 individuals of subclass C, 

 41.42 (+0.05). 



FREQUENCY TABLE III 

 Comparison of the Number of Fin-rats ix the 1918 and 1919 Broods op 



