21 6 WM. A. KEENER AND J. G. EDWARDS. 



as he suggested, it is highly probable that many, if not all of 

 Haeckel's Monera will be found to possess nuclei of this type. 

 Among flagellated forms it has been described by Biitschli ('96) 

 for Chromatium okenii and Ophidomonas jenensis, and by myself 

 ('98) for a species of Tetramitus. In the latter form the granules 

 of chromatin, which at first are scattered throughout the entire 

 cell with no apparent order, come together to form a loose aggre- 

 gate prior to division. In this condition the aggregate is divided 

 into halves, an equal portion going to each daughter-nucleus 

 (Fig. 2). It is important to note here, however, that another 

 element comes in to complicate the process. In the resting 

 condition of the cells, when the chromatin is distributed through- 

 out the cytoplasm, a faintly staining body can be found some- 

 where near the center of the cell (Fig. 2, A}. This body becomes 

 more definite as the chromatin granules come together for 

 division, and it divides into equal portions before the nucleus is 

 halved. During the process of division the chromatin granules 

 become heaped about this partly divided body, one half of which 

 remains in the center of each daughter-heap of granules until 

 the end of the division (Fig. 2, D-E). After division the granules 

 again separate, forming the distributed nucleus. The central 

 body, therefore, has the attributes of an attraction sphere. 



"The chromatin represented by this temporary aggregation 

 of chromatin granules about the sphere is permanent in the 

 majority of the Flagellates, and may perhaps be regarded as the 

 usual condition of protozoan nuclei. Among some Flagellates 

 the aggregation of chromatin granules about the sphere, al- 

 though permanent throughout resting and active phases, re- 

 sembles the loose aggregation of the division period of Tetramitus 

 in having no nuclear membrane (Chilomonas paramcecium, 

 Trachelomonas lageuella and T. kispida)" Again Calkins ('01) 

 speaks of what others take to be a nucleus as a division center: 

 "The flagellate Tetramitus shows an apparently similar division- 

 center. During the resting phases, the chromatin is distributed 

 throughout the cell, while an indefinite 'achromatic mass' 

 appears to be in direct connection with the cytoplasmic reticu- 

 lum. Immediately before division, however, the chromatin 

 granules collect about this body, and then, save for the absence 



