4IO MOXTGOMERY. [Vol. XV. 



mass of irregular granules within the nucleus appears to stand 

 in some relation to the growth of the nucleoli, at least there is 

 a relatively greater amount of this substance in the larger 

 nuclei ; it envelops the largest nucleoli and imbibes the same 

 stains, though more faintly, with which the nucleoli become 

 stained. Now as the gregarine grows, at the same time both 

 nucleus and the total mass of nucleolar substance increase in 

 size ; but the nucleus cannot grow without the addition of a 

 substance or substances to it, which have been derived from 

 without. Accordingly, I suppose that the substance of these 

 granules has an extranuclear origin, a substance, i.e., which, hav- 

 ing penetrated the nucleus from the cytoplasm, undergoes a 

 chemical change in the nucleus and there becomes precipitated 

 in the form of granules, for no such substance occurs in granu- 

 lar form in the cytoplasm. The growth of the nucleoli might 

 then be explained on the assumption of the intussusception of 

 this substance by the nucleoli. This explanation is offered 

 merely as a hypothesis, since I cannot prove its correctness 

 with the limited material at my disposal. Since no chromatin 

 was demonstrable in these nuclei, it remains for future workers 

 to show whether the chromatin is in these stages commingled 

 with the nucleolar substance, or whether it is represented by 

 one of the two substances of which some of the nucleoli are 

 composed ; and if so, whether all, or whether only a certain 

 number, of the nucleoli are thus partially constituted of 

 chromatin.^ 



C. Metazoa. 



a. Egg Cells. 

 I. Montagiia pilata {Ntxx.'). 

 (Plate 22, Figs. 57-63, 65-87.) 



In the germinal vesicles of this mollusc two kinds of nucleo- 

 lar structures occur : the true nucleolus, which is of large size 

 and almost invariably single ; and certain secondary structures, 



^ For observations of other authors on nucleoli in Gregarinida, cf. the reviews 

 of Minchin ('93), Van Beneden ('69), Marshall ('92), Frenzel ('93), Koelliker 

 ('49), A. Schneider ('75, '83), Welters ('91), Carnoy ('84). 



