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I>sTr»TANA UNIVERSITY 



2. The Effect of Starvation for Fn^ Successive Generations 

 ON THE Sex-Ratio in Drosophila Ampelophila. 



Claude DuVall Holmes. 



Introduction. — -Born^ and Ynng^ concluded that nutrition is 

 a determining factor of the sex-ratio, an abundance of food 

 leading to the development of a large proportion of females. 

 Cuenot^, using the larv.T of the same animals (Rana temporaria), 

 got contradictory results. He concluded, therefore, that food is not 

 a determining factor of the sex-ratio. Kellog and Bell*, using 

 the larvae of silkworms (Bomtyx mori), studied the possible effect 

 of feeding, with special reference to the influence it had on the 

 second generation. In their experiment, as they themselves say, 

 they did not succeed, by a reduction of the food-supply, in pro- 

 ducing any unmistakable results in the way of an over-production 

 of males. Furthermore, the numbers in each of their experiments 

 were too small to be of value. Kellog and Bell's experiment 

 involved two generations, so that they varied the food of the grand- 

 parents and that of the parents of the generation in which the 

 ratio was determined. Below I have reproduced their table, which 

 summarizes their results : 



KELLOa AND BELL'S TABLE. 



Lot. 



Fed. 



Parents. 



Grand- 

 parents. 



Deaths 

 Before 

 Maturity. 



Males. 



Females. 



1 



O 



0 



0 



2 



13 



10 



2 



M 



O 



O 



2 



U 



9 



3 



0 



M 



0 



3 



8 



14 



4 



M 



M 



0 



6 



8 



11 



5 



0 



0 



M 



0 



15 



10 



6 



M 



O 



M 



0 



11 



14 



7 



O 



M 



M 



20 



2 



3 



8 



M 



M 



M 



21 



2 



2 



Note.— O means optimum food supply. M means minimum food supply. 



It seemed, therefore, that an experiment in which the food factor 

 was varied for a greater number of generations back, and with a 

 form that furnished a larger number of individuals, was highly 



1 G. Born. Experimentelle Untersucliungen iiber die Entstehung der Geschlechts- 

 unterschiede^ Breslauer ArztUche Zeiischrift, Bd. Ill, (1881). 



2 E. Yuno', De I'inliuence des variations du milieu physicochimique sur le deve- 

 loppement des animanx, Archives dei) Sciences physique et naiurelle, XIV, (1885). 



s L. Cuenot. Sur la determination du sexe chez les animaux, Bulletin Scie^iflflque 

 de la France et de la Belgique, XXXII, (1899). 



4 V. L. Kellog and R. G. Bell, Notes on Insect Bionomics, Journal of Experi- 

 mental Zoology, i, (1904). 



