METHOD OF CELL DIVISION IN MONIEZIA. 143 



Concerning the structure of the nucleolus more can be seen 

 during the growth period than at any other stage of development. 

 In favorable preparations, the nucleolus in oogonia, oocytes and 

 segmentation cells shows a peripheral portion stain : ng violet 

 with the triple stain, and a central portion, the so-called vacuole, 

 staining with safranin. During the growth period additional 

 details appear. These are (Figs. 28-30), within the vacuole, a 

 small more or less refractive body, the endonucleolus (cf. Mont- 

 gomery, '99), staining very dark with gentian violet, a reticulum 

 supporting this body, and in the outer peripheral portion of the 

 nucleolus certain darker bodies. Certain appearances here very 

 much resemble the conditions described in the karyosome cycle 

 of Diplodiscus by Cary ('09). There is, however, no parallel in 

 the deve opment. 



Only one true nucleolus is present in a cell. Besides this there 

 are frequently one or more chromatin bodies, karyosomes, which 

 with iron haematoxylin stain like nucleoli. But the gentian violet 

 or Ehrlich-Biondi preparations never show more than a single 

 true nucleolus. 



As to the nature of the true nucleolus there is not much evi- 

 dence. Young deplores the use of the term "nucleolus" and 

 calls the structure a "nuclear granule." It is from the nuclear 

 granules, he holds, that the nuclei develop; the granules in turn 

 arising de novo (probably) from a common "cytoblastema." 

 "Containing, as they do in many cases, most of the staining 

 matter of the nucleus, they represent rather the chromatin than 

 the true nucleoli." I am obliged to dissent from this view; they 

 are without doubt true nucleoli, as differential staining shows. 

 Nevertheless, in addition to their nucleolar character they may 

 well serve as chromatin reservoirs during the resting period of 

 the nucleus. Indeed, the peripheral portion stains with gentian 

 violet just as does chromatin, and the darker bodies easily sug- 

 gest chromatin masses. The fact that the nucleoli increase in size 

 like the other elements of the cell during synapsis is explained by 

 the swelling of the vacuole, for this occurs markedly; in many 

 cases several vacuoles are present. Furthermore, the nucleoli 

 are always in intimate connection with the spireme, and of course 

 they disappear when mitosis comes on. C. v. Janicki ('03) finds 



