i!*!'^] Michael: Sagitta cnlifoniira from San Diego Region 117 

 TABLE 9 



('ORRELATION BETWEEN LENGTH OF ANIMAL AND NUMBER OF PoSTF.RIOR TeETH 



Total 3 6 6 11 31 82 56 195 



(■ = 0.7506 ±0.02109 



the most teeth. Moreover when we consider the imnibers in 

 brackets the following facts are revealed : 



These facts mal^e it obvious that the histogram (text fig. 2) 

 is approximately true only for animals between 20 and 24 mm. 

 in length, and even here the approximation is slight, for the rate 

 of addition of teeth with an increasing length of animal is rapid. 

 This histogram, then, can only be regarded as specifically con- 

 stant when the population considered consists of a similar pro- 

 portion of individuals of the various lengths to that upon which 

 it is based. 



