Il6 MARGARET C. FERGUSON 



gating nuclei of Pinus results from both these processes. For, 

 while there is always a large quantity of linin in the egg-nucleus 

 and a comparatively small amount of chromatin, the size of the 

 chromatic spireme, when formed, seems disproportionate to the 

 entire bulk of the chromatin earlier existing in the nucleus. 



The chromatin continues to separate out from these nuclei 

 until a spireme, studded with irregular granules, lies just within 

 the wall of the sperm-nucleus, and a similar one arises directly 

 below in the egg-nucleus. Frequently the cytoplasm caught 

 between the two nuclei collects into spherical masses ; between 

 these spheres of cytoplasm the membranes of the two nuclei are 

 in close contact (fig. 225). Very soon the spireme of each 

 nucleus becomes coiled and regularly moniliform, and the chro- 

 matic band of the sperm-nucleus takes up a position along that 

 side of its nucleus which is nearest to the spireme formed in the 

 egg-nucleus. At this time, delicate, minutely granular threads, 

 some of which pass from nucleus to nucleus, appear in the 

 regions of the two chromatic spiremes. The rest of the achro- 

 matic contents of these nuclei is largely transformed into long, 

 comparatively heavy threads, which are furnished with innu- 

 merable granules. The two nuclei are still perfectly distinct 

 and the nucleolus of the egg-nucleus may persist at this stage ; 

 the nuclear membranes are yet present, although they are very 

 irregular in outline and have given way at several points (fig. 

 227). The nucleolus is not always present at this time, but 

 nucleolus-like masses, which from their position are evidently 

 derived from the egg-nucleus, may be present as late as the 

 telophase of the division. Delicate, granular fibers continue to 

 arise in the regions of the two spiremes ; the coarser, achroma- 

 tic threads of the nuclei become finer in structure, and extend 

 in all directions toward the forming spindle; and the nuclear 

 membranes fade entirely out, not only along the line of contact 

 of the two nuclei, but from their entire outer surfaces as well 

 (fig. 227). Blackman states that, while the chromatic portions 

 of these nuclei remain distinct in Pinus sylvestris^ the nuclei 

 fuse at an early stage in the prophase of the division. There 

 is, apparently, no such fusion of the sexual nuclei in the species 

 of pines studied by the writer ; but the entire membrane of each 



