1 64 MUNSON. [Vol. XV. 



25. Occasionally the outer part can be seen to be radially 

 striated, so that when the central body is present the nucleolus 

 has the main features of a centrosome and a sphere. 



26. Such a structure is sometimes to be observed in addition 

 to a second homogeneous nucleolus. 



27. When the central body e.xists, there may be a network 

 surrounding it, which in turn is enclosed by the outer layer of 

 the nucleolus. 



28. In such cases the nucleolus has all the features of a 

 germinal vesicle, with nucleolus network and nuclear membrane. 



29. The nucleolus can be seen as long as the egg remains in 

 the follicle, but not after its discharge. 



30. In the later stages it is often very large and stains deeply. 



31. It may, however, become honeycombed with large 

 openings. 



32. In such a condition it may be accompanied by a very 

 much smaller one, apparently more perfect, and, like it, staining 

 deeply. This distinguishes it from the somewhat numerous 

 " Nebennucleoli " that are spread throughout the germinal 

 vesicle, and in carmine stains have a yellow coloration. 



33. The nucleolus may, therefore, consist of three different 

 •constituents : {a) linin framework ; (b) substance resembling 

 chromatin ; (c) substance resembling mature yolk globules. 



34. Movements of the nucleolus are regulated by the linin 

 framework which permeates it. 



35. The nucleolus disappears as such when the egg is 

 discharged from the follicle, and when, as we shall see, an 

 entirely different process of growth of the egg takes place. 



36. The history of the nucleolus coincides with the period of 

 growth of the egg, i.e., while it remains in organic connection 

 with the parent organism. 



b. Literature. — An extensive literature on the nucleolus 

 exists, from which many similar observations could be cited. 

 We are reminded at once of the observations of Balbiani ('83) 

 and Aime Schneider ('75). 



I cannot accept Rhumbler's ('93) mechanical explanation of 

 the radial feature of the nucleolus, nor his equally mechanical 

 explanation of the endonucleoli. 



