776 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



Studies by W. M. Barrows of Variation in Number of Teeth 

 on Male Sex-Comb, and of Variation in Size. 



To determine whether long-continued inbreeding had affected the 

 variability of the character, number of teeth on sex-comb of male, Mr. 

 Barrows has examined individuals from three different inbred series, A, 

 M, and N, and from one stock not inbred, X. These experiments show 



TABLE XXI. 



Correlation in Number of Spines between Sex-combs of Right and 

 Left Legs, Sixth Inbred Generation, A Series. 



Left leg (x). 



Mean number of spines, left leg — A x = 10.93 

 " " " right leg = A y = 10.94 



Standard deviation . left leg = ax = 1.453 

 " " " . right leg = ay = 1.230 



Coefficient of correlation . . . . r = .022 -J- .061 



no appreciable effect of inbreeding. In every case the brood reared 

 under the best and the most uniform conditions has the highest average 

 number of teeth, irrespective of whether or not it is inbred. The same 

 may be said of variation in size. Inbreeding has diminished neither the 

 average size nor the variability in size. 



The series and generations studied were A 61, M3], JV 30, and XI. 

 The origin and history of the first three has been described in detail in 

 the earlier parts of this paper. Series X originated from two pairs of 

 flies caught in Cambridge in October, 1905. Series N died out for lack 



