68 bulletin: museum of comparative zoology. 



The cytoplasm outside the granular mass is abundant, but much 

 clearer than that of the surrounding spermatogonia. 



The study of a large number of testes of different ages in this and 

 other species has failed to show any other stages in these cells. They 

 always appear approximately the same except for the differences in 

 the condition of the granular mass surrounding the nucleus. 



Lying outside and surrounding the primary spermatogonia are 

 large numbers of connective-tissue cells (Plate 4, Fig. 67), which can 

 be easily distinguished from the spermatogonia by their smaller size, 

 the relatively small amount of cytoplasm, and the deeper staining 

 qualities of the nucleus. When the primary spermatogonia divide, 

 one of the daughter cells is usually forced out of the layer of cells sur- 

 rounding the apical cell. This cell then becomes intimately asso- 

 ciated with one or more of the connective-tissue cells, which form an 

 investment around it. This investment persists until the descend- 

 ants of the cell are converted into spermatozoa. 



Sutton (:00, :02) maintained that in Brachystola the spermatogonia 

 and the cyst cells have a common origin, and that in the earlier genera- 

 tions they are indistinguishable. I believe that the cells which he 

 at first (:00) took to be primary spermatogonia and later (:02) to be 

 the first generation of secondary spermatogonia are all, in reality, 

 connective-tissue cells. Sutton was unable to find any transitional 

 stages connecting these cells with the later generations of spermato- 

 gonia. In my own preparations of Dissosteira and other species of 

 the Acrididae, the two types of cells are always easily distinguishable, 

 and I have seen nothing to indicate a genetic connection. 



The investment of spermatogonia by cyst cells marks the transition 

 from primary to secondary spermatogonia, the spermatogonium with 

 the surrounding cyst cells forming the beginning of a spermatocyst. 

 The secondary spermatogonia divide mitotically in rapidly succeeding 

 divisions, the daughter cells remaining enclosed by the cyst wall. 

 It is thus evident that all the cells in each cyst are the direct descend- 

 ants of a single primary spermatogonium, which became surrounded 

 by a connective-tissue investment. At the distal end of each follicle 

 are always a number of cysts containing from one or two up to a large 

 number of secondary spermatogonia, according to their age. In 

 striking contrast to the primary spermatogonia, where adjacent cells 

 are often in very different stages, all the cells of a cyst are usually in 

 practically the same stage of developmeiit. 



Occasionally nuclei in the cyst wall can also be seen undergoing 

 mitosis. 



