90 bulletin: museum of comparative zoology. 



cies, but the longitudinal split often shows with almost diagrammatic 

 clearness. The chromatin granules are large, and can be clearly seen 

 arranged in pairs at nearly regular intervals along the linin thread. 

 Figures 49 and 50 show the spireme as seen from the distal pole, while 

 Figure 51 shows a cross section of the loops just below the point where 

 they are attached to the nuclear membrane. In addition to the mono- 

 some, the cut ends of fifteen or sixteen threads can be distinguished in 

 the section, which is the number we should expect to find, since there 

 are sixteen autosomes in the spermatogonia. In stage / (Fig. 52) 

 the loops open out as in the preceding species and tend to take a pe- 

 ripheral position. The chromatin granules break up into still finer 

 particles, and the longitudinal split becomes less evident. However, 

 in this species there is no such obliteration of the longitudinal split 

 as in Dissosteira, but throughout stage / it remains fairly distinct. 



2. Monosome. 



The history of the monosome during the growth period is quite 

 different from that in Dissosteira, but shows many points of resem- 

 blance to Melanoplus. However, owing to its greater size the changes 

 in the monosome can be followed to much better advantage in this 

 species. During stage a (Fig. 47) the monosome is an elongated, deeply 

 staining, homogeneous body enclosed in a separate vesicle. Rarely, 

 it is divided by a transverse constriction into two nearly equal parts. 

 In stage h there is little change in the appearance of the monosome, 

 but, as in the preceding species, it becomes enclosed within the common 

 nuclear membrane. In the following stage {c) (Plate 7, Figs. 125-128) 

 the monosome forms a more or less flattened plate, in which several 

 small vacuoles can usually be distinguished. A little later (stage d) 

 it begins to elongate (Figs. 129, 130) and a process grows out from' 

 one end. In the following stage (e) this process may reach a consid- 

 erable length (Figs. 134-132). During this stage the bipartite struc- 

 ture of the monosome becomes evident. One part is a flattened, 

 rounded or somewhat elongated body with smooth contours, and con- 

 tains numerous small vacuoles. The other part is of nearly the same 

 size but greatly elongated and distinctly granular. In fact it strikingly 

 resembles the spireme, except that the chromatin granules are larger 

 and crowded together more closely. Wlien the monosome lies at 

 some distance from the distal pole it is connected with it by means of 

 this elongated part (Plate 3, Fig. 49; Plate 7, Fig. 131). However, 

 if located near this pole, as is usually the case, the elongated part ex- 



