406 EDMUND B. WILSON. 



EXPLANATION OF PLATES. 



PLATE I. 1 

 (Pentatoma senilis.) 



FIGS. 1-3. Spermatogonial metaphase-groups; 4-6, first spermatocyte-division 

 in polar view; 7, early anaphase, the large bivalent also shown separately at the 

 left; 8-10, late anaphases; n, 12 the same in polar view, sister-groups from the 

 same spindle (the identification of X and Y not entirely certain); 13, second sper- 

 matocyte metaphase-group, with chromatoid body; 14-15, the same in side view, 

 chromatoid body absent; 16, the same, with chromatoid body near one pole. 



1 All the figures from camera drawings, enlarged about 2,500 diameters. A 

 designates the acrosome, B the large bivalent, b the small bivalent (or their 

 products), C the chromatoid body, N the Nebenkern or chondriosome-body, X 

 and Y the sex-chromosomes. 



