1919] Kofoid-S>r(Zi/: Tricltoiniiii i>Ii(i catnpanula 69 



(pi. 11, figs. 70, 73, 74), the nuclei beeomiug rounded or nearly so, 

 with a separation from the parade.smose and the centroblepharoplast 

 (fig. 75). The paradesmose loses its staining reactions and soon fades 

 out, apparently being resorbed, either in the cytoplasm or by the 

 centroblepharoplast complexes. The chromosomes in the meanwhile 

 undergo few or no changes, retaining a position at some distance from 

 the poles after the disappearance of the spindle fibers, which may 

 not occur until the nucleus has begun to round up. 



Telophase: The reorganization of the nucleus may take place 

 before the constriction of the cytoplasmic body (pi. 12, figs. 76, 79), 

 or it may be delaj'ed until after separation of the two daughter cells 

 (fig. 84). The heterochromosome may be found at this period lying 

 near the ends of the chromosomes opposite to their point of attach- 

 ment to the spindle fibers (pi. 11, figs. 73-75). 



A vesicle is formed about this (pi. 12, fig. 83), and the other 

 chromosomes become aggregated in the central part of the nucleus. 

 These gradually lose their parallel positions and become mingled in 

 a coarse network (figs. 83, 78, 81) which resembles in many respects 

 a similar stage of the prophase nucleus (pi. 6, fig. 16). The nucleus 

 may begin its migration away from the centroblepharoplast to the 

 posterior region of the body even before final constriction of the cell 

 (pi. 12, fig. 76), though this is usually delayed until the daughter 

 flagellates begin to assume their elongate, campanulate form. 



Discussion of Mitosis 



Observations on the division of the membei's of this unique genus 

 have been scanty heretofore. Foa (1904) describes and figures some 

 stages of this process in two species which she designates as Tricho- 

 nympha agilis forma minore and T. agilis forma maggiore. The stages 

 she has figured are strikingly similar to the same stages found in our 

 own material. 



In both of these species division is preceded by a rounding up of 

 the body and an anterior migration of the nucleus, followed by divi- 

 sion of the anterior, narrowed portion of the body, the "tubolo," and 

 the ectoplasmic zone of flagella. As these structures separate they 

 spin out between them a stout band, the external spindle {fuso 

 esterno). The internal spindle {fuso interno) is formed by fibers 

 arising from the ends of this, passing through the nuclear membrane 

 arid attaching themselves to the chromosomes. The remaining steps 



