26 GENETICS 



otherwise could be handled only in the most indefinite 

 way. 



List of Constants 



- Arithmetical Mean (A.M.) = 4.9 



Mode (Af ) = 5 

 ~_ Average Deviation (-A.D.) = .52 



Standard Deviation (cr) = .846 

 . Coefficient of Variability (C. V.) = 1 . 72 



Formulae 



30 



25 



20 



15 



10 



A.D. 



S = sum 



x = deviation of the class from A.M. 

 f = number in the class 

 _ = totoZ number 



Number of Rays 2T 3 4 5 6 7 



FIG. 5. The fluctuating variability of starfish rays. From data by 

 Goldschmidt. 



Thus in this instance the arithmetical mean, ex- 

 pressed by the hypothetical number 4.915, a number 

 which of course does not actually occur in nature, is 



