ROBERTSON: THE CHROMOSOME COMPLEX. 279 



SYRBDLA ADMIEABILIS. 



cyte stages, as shown by their increased size. The chromatin 

 of the ordinary chromosomes seems to be strung out in gran- 

 ules along the linin threads, giving a somewhat bead-like ap- 

 pearance. The accessory, instead of being elongated and 

 stretched upon the nuclear wall as before, seems now to be 

 massed into a sort of irregular lump, which, however, still 

 clings to the wall. The nucleoli here stain deeply with the 

 safranin. In each of the four cells (figs. 12-15), all of which 

 are from the same cyst, two nucleoli seem still to be present. 

 Sometimes they lie very close together, even in contact (figs. 

 14 and 15). In addition there is in some cells, but not in 

 every one, another body {K, figs. 11, 12, 13) somewhat similar 

 to the others but more irregular and diffuse than they. It may 

 possibly be a portion of a chromosome that has not entirely 

 disintegrated or loosened up since the last mitosis, or it may 

 be a spermatocyte chromosome condensing ahead of its fellows. 

 At the proximal end of this follicle, where the cells are older 

 and farther advanced, and from which figures 10-15 were 

 taken, there is present only a single nucleolar structure, be- 

 sides the accessory, in each nucleus. The nuclei here, how- 

 ever, were not very well stained, so figures 16-22 were taken 

 from the proximal part of another follicle of the same testis. 

 They show the same stages as the preceding follicle, but much 

 better stained. 



In the spermatogonia, and in the earlier stages of the 

 growth period, as I have before indicated, there appear to 

 be two nucleolar bodies present. In the later growth stages 

 (figs. 16-26) there is only one that is at all a permanent 

 structure. This is about equal in size to two of the former 

 nucleoli. (Compare figures 14, 15 and 18.) From these ob- 

 servations it seems possible that there may be a conjugation 

 of these structures in the earlier stages to form the single 

 structure of the later stages. But the proof of the point 

 will have to be established by further investigation. The 

 single nucleolar body, as it occurs in the later stage, may 

 be distinguished from the accessory in three ways : (a) by its 

 smaller size; (6) by the fact that it usually lies nearer the 

 center of the nucleus, not against the nuclear wall, as does the 

 accessory; and (c) because in the later stages it gradually loses 

 its ability to hold the safranin stain (figs. 20-26) . The time at 

 which the body begins to lose its staining ability seems to 



