Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
0) 
The Sex Chromosomes. ar! 
Explanation of the Text Figures. 
The sex-chromosomes in Protenor (a—e), Euchistus (f) and Gelasto- 
coris (g). (The figures of Protenor and Gelastocoris from photo- 
graphs.) From Wilson, 1909 c. 
a, Side view, anaphase of second spermatocyte-division; b, c, polar 
views of the sister-groups from such a spindle; d, diploid (spermato- 
gonial) chromosome-group of the male; e, diploid chromosome- 
group of the female: f, second division of Euschistus; g, second 
divisions of Gelastocoris (Payne). 
Diagram of the relations of the sex-chromosomes (black) to sex- 
production. 
Semi-schematie figures of the sex-chromosomes as they appear in 
the differential division in various genera. X in white, Y in black. 
Diagram of the relations of the compound X-element to sex- 
production in various genera. X black, Y with eross-bar, ordinary 
chromosomes in white. The maturation-divisions of the female are 
here inferential only, not having been fully worked out in any of 
these forms. 
Diagram of the relations of the X-element in succesive generations. 
The X-element in outline is supposed to be responsible for a sex- 
limited character of the type shown in color-blindness. 
