1 62 MUNSON. [\oL. XV. 



within appears to receive additions from without. Thus a com- 

 paratively large hollow shell arises (PL XIII, Fig. 6). It would 

 appear almost as if the addition from without is in the form of 

 a precipitate, which becomes deposited on the surface of the 

 nucleolus. 



Owing to its relation to the linin network, which is often to be 

 observed within it, the nucleolus may be considered as having 

 a fixed position. Its movements within the germinal vesicle 

 must necessarily be regulated by the linin fibers which consti- 

 tute its framework. The " Nebennucleoli " appear to lie more 

 or less free in the meshes of the network. 



The main feature of both the " Hauptnucleoli " and the 

 " Nebennucleoli " can be seen in the living egg (PI. XVI, Figs. 

 io6, io8, 1 15-1 18). 



a. Summary on the nucleolus. — i. The nucleolus appears 

 at the time when the egg begins to grow. 



2. It arises as an irregular or spherical mass in an amorphous 

 stainable substance, surrounding the chromatin elements at the 

 time when the germinal vesicle assumes its specific character- 

 istics. 



3. There is usually only one, but occasionally there are two 

 in this early stage. 



4. As soon as it has assumed a definite spherical form, 

 it is differentiated into an outer zone enclosing a central 

 body. 



5. At first the entire nucleolus stains as readily as the 

 chromatin. 



6. The outer zone retains this power of staining, but the 

 inner body gradually loses it. 



7. The central body (endonucleolus or nucleololus) stains very 

 intensely in Heidenhain's iron-haematoxylin. With double 

 staining of the latter stain, combined with eosin, the entire 

 nucleolus can be seen as a red outer zone and a black or blue 

 central sphere. 



8. This central body may become elongated, so as to 

 protrude through the outer zone. 



9. It is extruded from the nucleolus, which then appears as 

 a hollow sphere with an opening at one pole. 



