336 PROCEEDINGS OF THE AMERICAN ACADEMY. 



With higher amplification, however, it is readily seen that this change is 

 due to the deposition of some of the chromatic threads upon the surface 

 of the nucleolus. These deposits are in the form of very diffuse spiremes, 

 which are similar to the segments which are still free in the nuclear space 

 (Figure 6). The nucleolus as seen in profile no longer presents an even 

 contour, but at the places where the dark areas are fouud the diameter of 

 the mass is increased (Figure 8 e). It is thus evident that loose threads of 

 chromatin are being merely applied to the outside of the nucleolus, not 

 embedded in its substance. The accessory chromosome still preserves the 

 same relation to the nucleolus as before, being closely apposed to one side 

 of this structure (Figure 8 d, e). 



As the cell continues to grow the free chromatin within the nucleus 

 becomes more and more scanty (Figures 6, 7), until soon only a few chro- 

 matin segments are to be seen where formerly there were many (Figure 7). 

 Finally, in the " vesicle " stage (Figures 9-13), no chromatin is to be found 

 in the nucleus except that which is massed about the nucleolus to form 

 the karyosphere. 



During the growth period of the spermatacyte the nucleolus has 

 increased very markedly in size ( Figure 8 e,f). This is due both to the 

 increase of nucleolar material and to the deposition of chromatin upon 

 the periphery of the nucleolus. At the time of the vesicle stage the 

 appearance of the karyosphere* varies considerably in different cells, this 

 variation being due to the different manner in which the chromatin is 

 arranged with regard to the nucleolus. Different appearances presented 

 by the karyosphere at this stage are shown in Figures 8/, and 9-13. 

 Usually the chromatin is distributed more or less unevenly over the sur- 

 face of the nucleolus ( Figures 8 f, 9) but often it forms a nearly complete 

 (Figures 11, 13) or complete (Figures 10, 12) layer about it, thus causing 

 the karyosphere to stain very intensely. In preparations stained with 

 haemotoxylin and Cougo red the karyosphere appears black when the 

 surface is in focus, but when the centre is in focus the middle portion of 

 the body shows a reddish-brown coloration, thus disclosing the presence 

 of nucleolar material. Likewise, when a portion of one side of the 

 karyosphere has been removed in the process of sectioning, the true 

 structure of the body is shown. Figure 10, representing such a condi- 



* In my former papers I have described the karyosphere as a highly organized 

 structure found within the nucleus and containing "chromatin (in a granular, 

 reticular, or spireme form), karyoplasm,— i. e., linin, — and karyolymph. It is in 

 fact a miniature nucleus." It is now seen that it may be still more complex, since 

 it may also contain nucleolar material. 



