OK THE GERM CELLS OF METAZOA. 163 



which are smaller than the others and more rounded are the chromatin nucleoli (Fig. 

 31, N. 3}. 



In the synapsis the fourteen chromosomes unite to form seven bivalent ones, and the 

 two chromatin nucleoli to form one bivalent chromatin nucleolus. The latter is periph- 

 erally placed in the nucleus, and not attached to the true nucleolus (Fig. 32). 



In a pole view of the monaster stage of the first maturation division are found eight 

 chromatin elements (Fig. 33) ; lateral view shows all are bivalent and dumbbell-shaped, 

 seven are chromosomes, and one easily recognizable by its much smaller size in the chro- 

 matin nucleolus (Fig. 33, N. 2). 



5. Peribalm limbolaris Stal. 



Two testes of this species were studied. 



In the rest stage (PL I, Fig. 34) and prophases of the spermatogonia are found two 

 chromatin nucleoli of unequal size (N. 2], and sometimes apparently three ; they are 

 generally not in mutual contact, though they are often apposed to the true nucleoli, of 

 which there are frequently two or three. 



In the spermatogonic monaster (Fig. 35) are sixteen chromatin segments, of which 

 the two smallest, rounded ones are the chromatin nucleoli ; the fourteen chromosomes are 

 notably elongated. 



In the synapsis the fourteen chromosomes unite to form seven bivalent ones, and the 

 two chromatin nucleoli to form one bivalent chromatin nucleolus; in the rest stage of the 

 spermatocytes (Fig. 36) the chromatin nucleolus (N. 2) is usually rounded and peripher- 

 ally placed, and generally unattached to the relatively very large true nucleolus (some- 

 times there are two true nucleoli, as in Fig. 36, rarely three). In the rest stage of the 

 spermatocytes there is a smaller chromatin nucleolus in addition to the larger one already 

 described, and this smaller may correspond to the third of the chromatin nucleoli found 

 sometimes in the rest stage of the spermatogonia. 



In the monaster stage of the first maturation division there are eight chromatin seg- 

 ments (Fig. 37), namely, seven bivalent, dumbbell-shaped chromosomes and one much 

 smaller bivalent, dumbbell-shaped chromatin nucleolus. 



6. Cosmopepla carnifcx Fabr. 



Five testes of this species were studied. 



In the monaster stage of the spermatogonia (PL I, Fig. 38) are found eighteen 

 chromatin segments ; two of these are smaller than the others, and so by analogy with 

 other species of this family probably represent chromatin nucleoli (N. 2, Fig. 38) ; the 

 sixteen other segments are then true chromosomes. 



