NUCLEI AND KINETIC ELEMENTS 95 



the actual cell nucleus or other easily recognizable organoid, should 

 be discarded together with the supplementary term trophonucleus. 

 The group Binucleata is sufficient evidence to show how far afield 

 we may be led by conceptions indicated by such misleading names. 

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

 t()])Iast" used by Wenyon, Dobell, and AlexeieflF, 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 Loplwmorias (Fig. 98, p. 212). Analogous structures 

 have since been found in practically all of the parasitic flagellates 

 thus far described, although not found in free-living t^-pes generally. 

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

 to the blepharoplasts of tj-pes like Tryixinosoma bnicei, Bodo edax 

 or Bodo lacertcB (Fig. 38) ; as an elongate mass in most of the Cryp- 

 tobia species (Fig. 47, C); as a long basal filament in Trichomonas 

 augiista (Fig. 72, p. 139) ; or Chilomastix mesyiili; as a spirally coiled 

 mass in Devescomia striata (Fig. 47, F.), etc. It apparently differs 

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

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

 or partly coiled or absent altogether. In Chilomastix mesniJi an 

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

 blepharoplast (Kofoid and Swezy, 1920. Fig. 45). 



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. 

 This substance, according to Kofoid, appears to form at the expense 

 of the nuclear cliromatin and increases or decreases— that is, the 

 parabasal body becomes larger or smaller apparently in relation to 

 metabolic demands. When the parabasal body is poor in chromatin 

 the blepharoplast and nucleus may be rich and vice versa. "Our 

 data are too incomplete to give a clear picture of the process, but 

 as far as they go they suggest the origin of the parabasal at the 

 expense of the chromatin of the nucleus, the movement of stain- 

 able substance on the rhizoplast, either to or from the blepharoplast 

 at the base of the flagella, and the wax and wane of the parabasal" 

 (Kofoid, 1916, p. 5). 



Kofoid's interesting and suggestive interpretation of the nature of 

 the parabasal is very well sustained by the morphological relations 

 of blepharoplast, nucleus and parabasal body in widely divergent 

 types of flagellates. INIorphologically, a series representing a 

 gradually increasing complexity is illustrated by (1) Ndgleria 

 gruheri, in which the blepharoplast arises by division of the intra- 

 nuclear kinetic center and remains connected with it bv a centro- 



