72 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
period of rest, the spermatogones seem to grow slightly, which is 
evident from the gradual increase in size of the cyst as a whole. (Com¬ 
pare pi. 15, figs. 64, 65, 66.) 
At rest the nuclei are large and spherical. An indistinct nuclear 
network is present, but the spherical chromosomes are arranged 
chiefly around the periphery (pi. 15, figs. 65, 66, 70). There is 
usually an indistinct, irregular, feebly staining body representing a 
nucleolus (pi. 15, fig. 65). But usually nothing can be seen except a 
deeply staining irregular mass of chromatin granules — a chromatin 
nucleolus. In mitosis this body disappears. It is probably an aggre¬ 
gation of chromosomes which assume their position at the equator 
of the spindle like the rest. 
Even these small spermatogones in the four- or eight-celled stage 
of the cyst show distinct and beautiful mitotic figures (pi. 15, figs. 66, 
67). Sections through the equator show twenty-eight chromosomes 
(pi. 15, fig. 66a). 
While in nearly all cases, all the cells of a cyst are in the same phase 
of mitosis, there are occasional exceptions (pi. 15, fig. 66b). These 
exceptions have aided me considerably in determining the rather 
obscure sequence of events. 
The original boundary of the nucleus can sometimes be seen after 
the nuclear membrane has disappeared and the spindle is fully formed 
(pi. 15, fig. 66c). There is no reason whatever to doubt that the part 
of the spindle lying between the outer circle of the eentrosome is 
derived entirely from the nucleus. This will be seen to be even more 
evident in the first maturation division. 
There is represented in plate 15, figure 67, an unusually distinct 
preparation showing the circles of microsomes surrounding each cen- 
trosome and the relation of the chromosomes to those circles. 
Synapsis .— When the cells of a cyst are nearing the end of the 
multiplication period, they pass through a series of changes which I 
have called synapsis, a term used by Moore (’ 95 ) to designate similar 
appearances in elasmobranehs. 
Up to this time, the spermatogones have remained spherical. Now 
they become crowded and consequently in tangential section regularly 
five-sided (pi. 15, fig. 70). They also become regularly arranged, 
acquire a conical shape, the apex being turned toward the center of 
the cyst, the base or broad end in contact with the enclosing cyst wall. 
In this broad outer part of the cell, the large spherical nucleus is inva¬ 
riably found (pi. 13, fig. 25). 
