THE MALE SOMATIC CHROMOSOME GROUP IN SCIARA PAUCISETA

Abstract

The present study is designed to furnish additional evidence bearing on the general problem of sex determination in Sciara. It is concerned particularly with two features. In the first place, evidence is given showing that in Sciara pauciseta Felt there are seven chromosomes in the male soma instead of eight as in the female soma, although the germ-line chromosome groups are alike in the two sexes. In the second place, it is shown that this evidence adds support to the hypothesis that the precocious 2 chromosome in Sciara is a sex chromosome (Metz, 1929, 1930). Earlier evidence bearing on the immediate problem may be summarized briefly as follows: 1. In all species of Sciara thus far adequately studied, the chiromosome group of the germ-line in both sexes (i.e., spermatogonia and oogonia) consists of symmetrical pairs of chromosomes-except for variations in the number of limited chromosomes which are found