10 



BULLETIN : MUSEUM OF COMPAKATIVE ZOOLOGY. 



Before describing the history of the spermatocytes, I will call atten- 

 tion briefly to the figures which illustrate their various conditions. The 

 earliest stage of spermatocytes that I have found is shown in Plate III. 

 Figs. 110, 111. In Figure 111 the cell is not complete, part of the 

 chromatin having been cut away in the previous section. Figure 221 

 (Plate V.) is of about the same age. Figures 114, 116 (Plate III.), and 

 184-186 (Plate IV.) give an idea of a slightly older stage. Figures 

 187, 188 (Plate IV.), and 222 (Plate V.) are still older. In these the 

 chromatic thread is already broken up into segments. Figures 228, 

 229, 242, 243 (Plate V.), and 175, 176, 178 (Plate IV.), show various 

 stages in the ring and " Vierergruppen " formation. During the first 

 spermatocyte division the chromatic Vierergruppen are arranged at the 

 equator of the spindle, essentially as shown in Figure 175 (Plate IV.). 

 Figures 237-241 (Plate V.) illustrate the first division of the sperma- 

 tocytes. 



The history of the spermatocytes of the first generation is as follows. 

 (Compare Diagrams 3 to 6 and 7 to 10.) In the earliest prophase that 

 I have seen (Plate III. Figs. 110, 111) the chromatic substance con- 

 sists of numerous small granules, already arranged along a thread of 

 substance, which itself stains somewhat (Diagram 3). The chromatic 

 granules gradually become collected at twenty-four points on the thread 

 (Diagram 4). The thread then breaks transversely into twelve seg- 

 ments (Diagram 5). Each of these segments has the form of a dumb- 

 bell, i. e. consists of two terminal chromosomes connected by a thread, 

 composed of numerous linin fibres (Plate IV. Fig. 187, Plate V. 

 Figs. 242, 243). 



