432 MONTGOMERY. [Vol. XV. 



the size of the nucleus, seldom small. It is the rule that in 

 one, sometimes in all the nucleoli, a large unstaining globule 

 is present, which has the appearance of a vacuole (Figs. 284- 

 287, 298) ; no nucleolus has more than one such globule. Quite 

 often there is only a single large vacuole-containing nucleolus 

 in a nucleus ; or there may be from one to six nucleoli, only 

 one of which contains a vacuole, and then the latter is usually 

 the largest ; or again, there may be two or three large nucleoli, 

 nearly equal in point of size, each of which contains a vacuole 

 (of course numerous intermediate stages may be found). There 

 is certainly a successive production of nucleoli, but it is diffi- 

 cult to decide whether some of these after leaving the periphery 

 of the nucleus fuse together, or whether some divide into smaller 

 nucleoli. Now it seems probable that those nucleoli which are 

 formed first are usually unequal in size, both in the same nucleus 

 and in different nuclei, as a comparison of the figures shows. 

 And though a gradual fusion of the nucleoli might play some 

 part in the youngest germinal vesicles, nevertheless it would 

 seem more probable that we have to do in these early stages 

 with divisions of the nucleoli, especially since in the following 

 stage they are much more numerous, as well as smaller. Fig. 

 287, in which three apposed nucleoli are to be seen, may thus 

 represent a division of a single nucleolus. It is not unlikely 

 that the unstaining globule within a nucleolus might aid, if it 

 is not the direct mechanical cause of, such division. This first 

 nucleolar stage is then characterized by the successive forma- 

 tion of a few comparatively large nucleoli at the periphery of 

 the nucleus, and the migration of these towards the center ; 

 the presence of large vacuoles within some of the nucleoli is 

 also a criterion of this period. 



Second nucleolar stage. — We find a group of numerous 

 nucleoli near the center of the nucleus, which are frequently 

 more numerous than in our Fig. 292. At this stage they 

 attain their smallest dimensions, and are approximately equal 

 in size ; they are completely homogeneous and contain no 

 vacuoles. The total number of the nucleoli is apparently 

 greater at this stage than at any other. 



Tliird nucleolar stage. — This is characterized by an increase 



