114 BIOLOGY OF THE PROTOZOA 



material the so-called kinetonucleus affords little evidence of nuclear 

 make-up ; it appears as a homogeneous mass of chromatoid material 

 which divides into equal parts prior to division of the nucleus. Such 

 features do not make it a nucleus any more than similar features 

 make nuclei of pyrenoids, or of other plastids of the cell. Func- 

 tionally, and unlike the nucleus, it is not necessary for the vital 

 activities of the organism, as shown by the experiments of Werbitski 

 (1910), confirmed by others, in which by the use of certain chemicals 

 (e. g., pyronine) the "kinetonucleus" of Trypanosoma brucei disap- 

 pears without any effect upon the movements and reproduction of 

 the trypanosome, a race being formed in which this organoid is 

 absent. Nor can the " kinetonucleus " be regarded as a centrosome, 

 for although closely connected with basal granules, it never behaves 

 like an attraction center. With the exception of Schaudinn's account 

 and the overdrawn account by Rosenbusch there is no evidence that 

 it divides by mitosis; it never develops chromatin structures which 

 by any stretch of the imagination can be called chromosomes. 



If the " kinetonucleus " is not a nucleus nor an active kinetic center 

 of the cell, then any misleading appellation such as kinetonucleus, 

 centrosome, or blepharoplast, which indicates co-partnership with 

 the actual cell nucleus or other easily recognizable organoid, should 

 be discarded together with the supplementary term trophonucleus. 

 Among names suggested to replace the term kinetonucleus is " kine- 

 toplast" used by Wenyon, Dobell, and Alexeieff, and "parabasal 

 body" (Janicki) as used by Kofoid. 



The non-committal term parabasal body was first employed by 

 Janicki (1915) to designate an accessory structure in the kinetic 

 complex of Lophomonas (Fig. 105, p. 211). Analogous structures 

 have since been found in practically all of the parasitic flagellates 

 thus far described, although not found in free-living types generally. 

 It is present as a globular mass of deeply-staining substance close 

 to the blepharoplasts of types like Trypanosoma brucei, Bodo edax 

 or Bodo lacertae (Fig. 33, p. 65) ; as an elongate mass in most of the 

 Cryptobia species (Fig. 61, C) ; as a long basal filament in Trichomonas 

 augusta (Fig. 77, p. 145) ; or Chilomastix mesnili; as a spirally coiled 

 mass in Devescovina striata (Fig. 62, F), etc. It apparently differs 

 in size and form in different phases of the same organism as in Bodo 

 lacertae where, in addition to the globular form, it may be rod-like 

 or partly coiled or absent altogether. In Chilomastix mesnili an 

 homologous rod-like body, termed the parastyle, arises from a second 

 blepharoplast (Kofoid and Swezy, 1920) (Fig. 60). 



The most extensive work on the parabasal body has been carried 

 out by Kofoid and his followers who regard this structure not as a 

 nucleus nor as a kinetic center, but as a "kinetic reservoir" or a 

 reservoir of substances which are used by the animal in its kinetic 

 activities under the conditions of its dense environmental medium. 



