162 



MONTGOMERY — A STUDY OP THE CHROMOSOMES 



in the monaster stage of the second division there are six univalent chromosomes, the 

 constrictions of which represent the reappearance of the longitudinal split (Fig. 26) ; 

 there are also in the same equatorial plate two non-constricted bodies of different volumes 

 which are not, joined together. These an; the chromatin nucleoli, which are regularly- 

 halved in the first maturation metakinesis — that is, they are the halves of univalent ones. 

 Thus the bodies marked N. 2 in Fig.. 26 are the halves of those similarly marked in 

 Fig. 25. 



The second maturation division is equatorial, and the spermatid receives six chro- 

 mosomes, arranged in an outer circle around a single central chromatin nucleolus. 

 Accordingly in this second division one chromatin nucleolus passes undivided into one- 

 daughter cell (spermatid), the' other undivided into the other (laughter cell. 



As in JEkchiatm variohrius, two follicles of the testis contain spermatocytes of a, 

 much larger size than those in (lie four other follicles. 



;>. Podisus spinosus Dal I. 



Five testes of this species were studied. 



In the spermatogonic rest stage there are two small chromatin nucleoli, of more or 

 less rounded form, attached to tin; surface of a, true nucleolus. 



In the spermatogonic monaster there arc sixteen chromatin segments (PL I, Fig. 

 27), two of winch, probably correspond to the chromatin, nucleoli of the previous rest- 

 stage. 



In the synapsis the fourteen chromosomes unite to form seven bivalent- chromosomes. 

 The two chromatin, nucleoli also come together to make one. bivalent one; in the growth 

 period of the spermatocytes (Fig. 28) the chromatin nucleolus lies close to the nuclear 

 membrane, and to its inner surface the (rue nucleolus is regularly attached. 



In the first maturation monaster there are eight, chromatin elements, namely, seven 

 chromosomes and one chromatin nucleolus, all bivalent, and dumbbell-shaped on lateral 

 view; the chromatin nucleolus has about, the same volume as the smaller ones of the 

 chromosomes, and so cannot be- distinguished from them with certainty. 



4. Mormidea lugem Fa-br. 



Five testes were studied. 



In the rest stage of the spermatogonia there are two chromatin nucleoli (PI. I, Fig. 

 30, N. #), which may be equal or unequal in size; they may be attached together, which 

 is apparently the general rule, or may be separated, and one or both of them may be 

 apposed to the true nucleolus. 



In the spermatogonic monaster there are sixteen chromatin segments; two of these 



