110 University of California Publications in Zoolngij [Vol. 20 



Its course in the prophase has not been followed but it apparently 

 retains its isolated position throughout. 



Telophase : As the two eentroblepharoplasts with their related 

 structures move towards opposite ends of the cell, the slender band 

 connecting the two halves of the nucleus becomes ruptured, while the 

 paradesmose fades out and begins to disappear at its middle portion 

 (pi. 14, fig. 21). The daughter nuclei at this time are spindle-shaped 

 both ends drawn out to a slender point, with the chromosome lying 

 in a roughly subparallel band near the center. The point of the 

 nucleus opposite the poles is withdrawn (fig. 20), the spindle fibers 

 disappear, and the nucleus loses its connection with the centro- 

 blepharoplast (fig. 18) and begins to round up. This part of the 

 process is usually completed before the chromosomes begin to undergo 

 reorganization (pi. 14, figs. 22, 23, 25). Plasmotomy may occur 

 before this takes place (fig. 25) or it maybe delayed until reorganiza- 

 tion of the nucleus and the reformation of the neuromotor system 

 of each daughter cell has been completed (fig. 24). 



RELATIONSHIPS 



The close similarity of the various phases of division, combined 

 with the striking resemblances in their morphological characters, 

 indicate at once a close relationship between Leidyopsis and Tricho- 

 nympha. These resemblances are found in the differentiations of the 

 ectoplasm, the neuromotor system, and the interrelations of its various 

 parts, the lack of a distinct cytostome, and the division of the endo- 

 plasm into a uniformly granular anterior portion and a posterior part 

 filled with coarse alveoli and food particles, indicative of holozoic 

 nutrition. 



The differences between these two genera are few, but are im- 

 portant from a taxonomic standpoint. The most striking one is found 

 in the number and arrangement of the flagella. In Trichonympha 

 these cover two-tliirds or more of the surface of the body and are 

 divided into three distinct groups, an anterior, middle and posterior 

 group. The anterior group is composed of long flagella, the middle or 

 lateral group, which is the largest in extent, of short, cilia-like flagella, 

 and the posterior group of flagella, which are twice or even three 

 times the length of those in the anterior group. In Leidyopsis the 

 middle and posterior groups of flagella are lacking, leaving only the 

 group of long flagella at the anterior end of the body. 



