1(54 MONTGOMERY A STUDY OF THE CHROMOSOMES 



In the synapsis stage of the growth period the sixteen chromosomes unite to form 

 eight bivalent chromosomes, and the two chromatin nticleoli to form one bivalent chro- 

 matin nucleolus. The latter is, in the rest stage of the spermatocytes, rounded and 

 peripheral in position, and is not attached to the larger true nucleolus (Fig. 39) ; both 

 the nucleolus and the chromatin uucleolus may contain a large, clear vacuole, which in 

 the former is excentric. 



Pole views of the monaster stage of the first maturation division show nine chroma- 

 tin elements (Fig. 41), and lateral views (Fig. 40) of the same stage show that all are 

 bivalent and dumbbell-shaped. The smallest of these elements is the chromatin nucleolus 



(N. 2\ 



7. Nezara hilaris Say 



Five testes of this form were studied. 



There are in the rest stage and early prophases of the sperniatogonia two chromatin 

 nucleoli, which are comparatively large and usually more or less unequal in size (PI. I, 

 Figs. 42, 43, N. 2). They are generally peripheral in position and in mutual contact, 

 but usually are not apposed to the true nucleolus (-ZV). 



In the spermatogonic monaster there are sixteen cliromatin segments (Fig. 44), of 

 which two can be always recognized by their small size and rounded form as the chroma- 

 tin nucleoli ; the fourteen chromosomes are generally elongated. 



In the synapsis the two chromatin nucleoli unite to form one bivalent one, and 

 apparently also the fourteen chromosomes join to make seven bivalent chromosomes, but 

 I cannot state this with certainty. In the telophase of the spermatocytes (Fig. 45), the 

 chromatin nucleolus (N. 2) is peripherally placed and clearly bivalent, and usually not 

 in connection with the very large true nucleolus (-ZV), which is also peripheral. 



In the testes examined (all from individuals secured in the month of September) 

 were stages only from the resting sperniatogonia to the telophase of the spermatocytes ; ; 

 all later stages in the spermatogenesis were absent, so that the number of the chromosomes 

 in the maturation divisions could not be determined. 



The longitudinal split in the chromosomes during the growth period is unusually 



distinct in this species. 



8. Brochymena sp. 



Three testes of this species were studied. 



In the rest stage of the sperniatogonia (PI. I, Fig. 46) are two small chromatin 

 nucleoli (N. 2), which are peripheral in position, of nearly equal size, generally mutually 

 apposed, and seldom attached to the true nucleolus. 



In the spermatogonic monaster stage (PL I, Fig. 47) are sixteen chromatin segments, 

 of which two are smaller and rounded and are the chromatin nucleoli. 



