238 N. M. STEVENS. 



The Bryn Mawr Diabroticas of 1907 were all collected on a 

 large clump of golden rod in a pasture that had not been culti- 

 vated for many years, and they may have come out of the ground 

 in the immediate neighborhood or from more recently cultivated 

 fields near by. 



These erratic sex ratios are probably merely another example 

 of the interference of external conditions in what would otherwise 

 be an equality of sexes, or in other words a shifting of normally 

 equal sex ratios, or partial exclusion of one sex by peculiarities 

 in the environment. The collections were all random in the 

 sense that all the individuals that could be found were collected 



each time. 



BRYN MAWR COLLEGE, 

 January 3, 1912. 



LITERATURE CITED. 

 Schleip, W. 



'n Uber die Chromatinverhaltnisse bei Angiosiomum (Rhabdonema) nigro- 



venosiim. Ber. d. Naturf. Gesell. Freiberg i/B, XIX. 



'n Das Verhalten des Chromatins bei Angiosiomum (Rliabdom-ma) nigro- 

 venosum. Ein Beitrag zur Kenntnis der Beziehungen zwischen Chromatin 

 und Geschlechtsbestimmung. Arch. f. Zellforsch., VII. 

 Stevens, N. M. 



"08 The Chromosomes in Diabrotica vitlala, Diabrotica soror and Diabrotica 

 12-punctata. A Contribution to the Literature of Heterochromosomes and 

 Sex Determination. Journ. Exp. Zool., \ . 

 Wilson, E. B. 



'09 Studies on Chromosomes, V. The Chromosomes of Melapodhis, a Con- 

 tribution to the Hypothesis of the Genetic Continuity of Chromosomes. 

 Journ. Exp. Zool., VI. 



