442 MONTGOMERY. [Vol. XV. 



mencement of this first nucleolar stage the nucleolar substance 

 appears at only one point in the periphery of the nucleus, and 

 always in the shape of an irregular mass. 



Second nucleolar stage. — This period is characterized by 

 the formation of other nucleolar masses at various points in 

 the periphery of the nucleus, the successive detachment of all 

 of these from their connection with the nuclear membrane, and 

 their migration towards the center of the nucleus. The com- 

 mencement of this process is to be seen in very young nuclei, 

 where but a single peripheral nucleolar mass is present ; from 

 the inner side of this mass small particles become divided off 

 (Figs. 219, 224, 225), then each of these particles assumes a 

 more or less spherical shape and wanders to the center of the 

 nucleus ; this process continues until the whole mass of nucleo- 

 lar substance has reached the center in the form of separate 

 particles (Figs. 217, 218, 223, 227). The peripheral nucleolar 

 mass usually stains less intensely than the portions which have 

 already reached the center of the nucleus. While the first-formed 

 peripheral nucleolar mass is thus gradually wandering to the 

 center, other masses are successively forming at the periphery 

 of the nucleus, and their detached portions successively passing 

 to the center. When a considerable number of these nucleoli 

 have reached the center of the nucleus they naturally come 

 into mutual contact, and then a process of fusion sets in, which 

 results in the coalescence of neighboring groups of nucleoli, so 

 that a smaller number of larger ones are formed. Sometimes 

 this fusion may proceed to such an extent that one single, 

 enormous nucleolus results (Fig. 226), but usually several 

 large nucleoli are the result, these being unequal in size. 

 The irregularity both in the dimensions and the forms of the 

 nucleoli is particularly characteristic for this stage ; thus the 

 individual nucleoli often have elongated processes and angles, 

 and this irregularity is frequently so excessive that the nucleoli 

 within the nucleus appear like smears of ink upon a page (Figs. 

 226, 227, 230). I think that this irregularity in form may be 

 explained by the assumption that at this stage the substance 

 of the nucleoli is viscid in its consistency, while in the follow- 

 ing one, where the spherical form is the rule, its nature must 



