NUCLEAR DIVISION IN PROTOZOA. 



221 



Uis the sphere becomes more compact and distinct during the 

 preparatory division stages, while the chromatin granules col- 

 lect in a small aggregate in its immediate vicinity. The sphere 

 then divides, and the chromatin aggregate separates into two 

 portions. This stage in the division probably corresponds to 

 the stage described by Schaudinn for the swarm spores of 

 Paramceba, where the chromatin granules form a ring about the 

 divided sphere, for, in a later stage, the chromatin granules are 

 closely aggregated about the daughter-spheres {cf. Fig. 2, E). 

 Here, also, Schaudinn describes the sphere (his Nebenkbrper) 



Fig. 3. — Development and division of the swarm spores of Paratnceba Eilhardi (after Schaudinn). 



as a portion of a similar body in the cytoplasm of the parent 

 Amceba, from which it arises by repeated division. The swarm 

 spores increase by binary fission, the sphere dividing first, as 

 in Tetramitus. The nucleus, which is a permanent aggregate 

 of granules, then moves around the connecting strand of the 

 daughter-spheres, until, like the central spindle of Noctiliica, 

 it is entirely surrounded (Fig. 3). The connecting strand of 

 the daughter-spheres of Paramcsba is homologous, therefore, 

 with the central spindle of Noctihica and of the Metazoa. 

 After division the sphere lies upon the outside of the recon- 

 structed nucleus, as in the resting cell of Noctihica. 



correspond in function to the sphere, although I have not been able to follow 

 this body in division. 



