OF THE GERM CELLS OF METAZOA. 185 



another, but separated from the nucleolus (Fig. 162) ; (3) the chromatin nucleoli sepa- 

 rate from one another, and only one in contact with the nucleolus (Figs. 163, 165) ; (4) 

 the chromatin nucleoli separate from one another and from the nucleolus ; (5) the 

 chromatin nucleoli separate from one another, but both attached to the nucleolus (Fig. 

 164). These conditions do not appear to be stages in position, but rather individual 

 variations. Whenever the two chromatin nucleoli are mutually apposed, it is never an 

 intimate apposition i. e., they never fuse to form one large rounded one such as is the 

 general rule in the Pentatomidce. Through the rest stage of the spermatocytes each 

 chromatin nucleolus remains elongate (they appear round only when seen from the end). 

 Sometimes each shows a trace of a transverse constriction, and in one case (Fig. 165) one 

 of them was separated into two parts. 



Through the prophases of the first maturation mitosis the chromatin nucleoli remain 

 separate from one another, and each is elongate in form (Fig. 166, N. 2, showing also all 

 seven bivalent chromosomes on lateral view). 



Pole views of the monaster stage of the first maturation division show in most cases 

 nine chromatin elements (Fig. 167) ; the seven larger ones are chromosomes, all bivalent 

 and on lateral view dumbbell-shaped (Fig. 166); the two smaller, centrally placed ones 

 are the two chromatin nucleoli (N. 2, Fig. 167). In one case, ten elements were seen on 

 pole view (Fig. 168) ; this is very unusual, but it may probably be explained by the 

 assumption that there are here two chromatin nucleoli, six bivalent chromosomes, and 

 two univalent chromosomes formed by the precocious separation of the parts of a biva- 

 lent chromosome. A lateral view of the spindle is given (Fig. 169), showing the two 

 chromatin nucleoli, but only two of the seven bivalent chromosomes. 



In the metaphase of this mitosis all seven chromosomes become transversely divided 

 (reduction division), and each of the chromatin nucleoli becomes also divided in a plane 

 perpendicular to its long axis (compare Figs. 169 and 170, in each of which only two of 

 the seven chromosomes are shown). A pole view of one cell of the dyaster stage followr 

 ing (Fig. 171) shows the two daughter chromatin nucleoli (N. 2) and the seven daughter 

 (univalent) chromosomes (the apparent transverse constrictions on them representing the 

 reappearance of the original longitudinal split ; compare the left-hand chromosome of 

 Fig. 170). 



The behavior of the chromatin nucleoli is thus different from that of the other 

 Hemiptera examined in the following regards : (1) their large size in the spermatogonic 

 monaster (Fig. 160), so that they can hardly be distinguished in volume from the 

 chromosomes ; (2) the phenomenon that they remain more or less separate from one 

 another during the growth period of the spermatocytes (Figs. 161-165) and prophases 

 of the first maturation division (Fig. 166) ; (3) the fact that one or both may appear 



