Studies on Chromosomes. 



38 



n, o, /?). Each spermatid-nucleus thus receives seven chromo- 

 somes, one-half the spermatogonial number, and no accessory 

 chromosome, in the usual sense of the word, is present; but the 

 spermatids nevertheless consist of two groups, equal in number, one 

 of which contains the smaller, the other the larger of the idiochro- 

 mosomes. In the mature spermatozoa I have not been able to 

 detect any corresponding difference. 



a 



d 



f 



b 



M 



I 



m 



FIG. 3. 



Euschistus fissilis, Euschistus sp., Podisus spinosus. a-c, Euschistus fissilis. a, metaphase- 

 group, first division; b, c, metaphase-figure, and early anaphase in side view, second division, d-i, 

 Euschistus sp.; d, e, metaphase groups, first division; /, metaphase-group, second division; g, second 

 division, side view; h, i, daughter-groups, late anaphase of second division, from the same spindle; 

 j-m, Podisus spinosus; j, metaphase-group, first division; k, late anaphase, second division; /, m, 

 daughter-groups from the same spindle, late anaphase, second division. 



In Euschistus, Brochymena, Podisus and Trichopepla the facts 

 are, with a few variations of detail, essentially similar. In both 

 species of Euschistus and in Brochymena the number of chromo- 



