232 University of California Publications in Zoology [Vol. 16 



So far as the actual facts which bear on the nuclear value of the 

 parabasal boch' are concerned, a few definite statements may be made. 

 In all the results of investigations in this field which it has been pos- 

 sible to examine, not the slightest evidence has been found to justify 

 the current practice of attributing to the parabasal body nuclear hom- 

 ology, function, or behavior. It is a structure which is not composed 

 of nuclear chromatin, and hence cannot carry on the functions of that 

 organelle. It is not a kinetic center, for all kinetic activities are car- 

 ried on, for a time at least, with undiminished vitality after its total 

 disappearance from the cell. As Janicki (1911) has suggested in the 

 case of the parabasal bodies of the Trichonymphida, these structures 

 are probably reserve material connected with the very great kinetic 

 activity of the cell. Its relation to kinetic activities is thus wholly 

 secondary. 



IV. Use as a Basis for Classification Not Critically Defendible 



The classification of the Protozoa must be based upon well-defined 

 characteristics of as great permanency as possible, correlated with full 

 consideration of the life-cycle as a whole. This is especially necessary 

 in those forms in which an alternation of generations occur. 



An examination of the order Binucleata shows that, in the first 

 place, it is founded upon an hypothesis, the binuclear theory, which, 

 in its essential point, has been contradicted by the results of Wer- 

 bitzki (1910), Kudicke (1911) and others, in proving that the para- 

 basal body is not composed of nuclear chromatin. This is positive evi- 

 dence and must stand until some further test shall show that the two 

 structures are identical in composition. 



In regard to the claim that the parabasal body ever arises de novo 

 by a heteropole division of the nucleus, not a single in.stance, critically 

 proven, have I been able to find of its actual occurrence, either in the 

 literature, or in working over the organisms themselves. And like- 

 wise it has been impossible for any workers subsequent to Schaudinn 

 (1904) to detect its de novo origin among the trypanosomes in a 

 single instance. It seems to be a constant, permanent cell organ in 

 these flagellates, passed on by division in each mitosis. Its fate in 

 gamete formation and its subsequent history in the zygote awaits the 

 critical analysis of those stages, if they occur, in these flagellates. 



These two points cover the only reason for forming the order 

 Binucleata in the first place, namely, that these organisms possess two 

 distinct nuclei, both composed of "lokomotorische-generative" and 



