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THE AMEBIC AN NATURALIST [Vol. XLIX 



There is no evidence in favor of parthenogenesis resulting in a smaller 

 variability than sexual reproduction, for if the workers be more, the 

 queens are less, variable than the drones. 



It was suggested by the writers that the large variabilities 

 of the workers might have resulted from subclasses 

 among them due to differentiated functions or nurtures. 



Castle, Carpenter, Clark, Mast and Barrows ( '06) made 

 observations on the variability and fertility of Drosophila 

 ampelophila Loew, the small fruit fly, as modified by in- 

 breeding and cross breeding. They found that " inbreed- 

 ing does not affect the variability in number of teeth on 

 the sex comb of the male, nor the variability in size." 

 While the conclusion is not in accord with an earlier ob- 

 servation (p. 780) that variability would seem to have 

 been increased by inbreeding so far as a comparison of 

 the sixth inbred generation with the sixty-first genera- 

 tion, the small number utilized in the sixth generation 

 (40 males in series A-6, B-6, C-6 each) was ground for 

 the opinion that such a conclusion had little value in com- 

 parison with data pointing in the reverse direction. If 

 however we calculate the coefficient of variation for the 

 length of the tibia, an unfortunate omission on the part 

 of the writers, it may be noted that the flies produced by 

 inbreeding are decidedly more variable than those pro- 

 duced by cross breeding. Data for this conclusion are 

 given in a subsequent part of the present paper. 



Walton ('08) noted that the results of measuring zygo- 

 spores of Spirogyra indicated that the close-bred indi- 

 viduals were more variable than the cross-bred individuals 

 and furthermore that the data went far toward confirm- 

 ing the theory that sex existed for the purpose of limiting 

 instead of augmenting variability. 



Emerson ('10) found that crosses between races of 

 plants (maize, squash, beans, gourds) differing in size and 

 shape had the variability of the second (F 2 ) generation 

 approximately twice as great as the variability of either 

 parental form or of the first (F,) generation. This he 



