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INDIANA UNIVERSITY 



No special attempt was made to get the sex-ratio of the starved 

 flies in the several generations, the only point being to get suffi- 

 cient males and females to carry on the successive generations ; 

 but such as came off were kept and their ratio included in the 

 tables. In the sixth generation, however, relatively large numbers 

 were reared with the view of ol)taining a measure of any modifica- 

 tion of the sex-ratio that may have occurred as the result of five 

 generations of starvation. 



Results. The details of the lineage of the five strains are given 

 in Tables I, II, III, IV and Y. The ratios given, except in the 

 sixth generation, are based for the most part on small numbers. 

 These Avere mostly starved individuals. Strain -t proved very un- 

 productive, and so was discontinued after the thir.d generation. In 

 Table YI all the data for the fi^'e strains are summarized. 



The normal sex-ratio of these flies, as determined by Dr. W. J. 

 Moenkhaus in a count of over tliirty thousand individuals reared 

 under normal food conditions, was found to be 100 d^'s 112 ^ 3. In 

 the first generation of this experiment the ratio was 100 : 108. We 

 may, therefore, be certain that the normal sex-ratio is approxi- 

 mately, 1 : 1.08. It will be seen by inspection of the ratios during 

 the first five generations that they remained approximately the 

 same. Any considerable deviation from the normal can readily 

 be ascribed to the small number of individuals involved. Thus 

 in the second generation the ratio changed to 1 :.82. with only 

 thirty-one individuals. As previously stated, only in the sixth gen- 

 tration were a large number of offspring reared. In this genera- 

 tion a total of 4,733 individuals were obtained from four of the 

 strains, strain 4 having been discontinued. The ratio of the total 

 Avas 1 : 1.14 (2,2] 3c^'s, 2,520 9 's) . Approximately the same prepon- 

 derance of females obtained in the individual strains, except in 

 Strain 3, where the ratio Avas 1 : 1.34, Avith 912 indiAdduals in- 

 volved. An explanation of this unusual ratio could only be con- 

 jectural; the AAT^iter does not regard it as significant. The experi- 

 ment is complete up to the sixth generation, but the breeding AA-as 

 continued in a somcAA^hat desultory AA^ay for three more generations. 

 These add nothing to the result except a larger final total from 

 all the strains. This larger total, 9,874 indiA^duals. again. shoAvs a 

 ratio (1:1.12) approximately equal to the original ratio. 



Conclusions. 1. Rigid starvation for five (ten^ generations 

 does not influence the sex-ratio in Drosophila. 



