1920] KofoidSwezy: Morpholofjy and Mitosis of Chilomastix 127 



above and also of a sucker or holdfast action of tliis region which we 

 have occasionaly seen in the free flagellates. The structure, lateral 

 position, and relation to the cj'tostome of this parabasal suggest its 

 analogy to the antero-laterally located, deeply stained, curved struc- 

 ture near the rim of the cytostome of Giardia, wilich we have called 

 the anterior peristome (Kofoid and Christiansen, 1915), but we 

 believe it to be the homologue of the parabasal, and that the peri- 

 stomal fibers of the two genera are homologues. It appears to bear 

 the same morphological relation to the cytostomal flagellum that the 

 parabasal bears to the undulating membrane in Trichomonas. Chal- 

 mers and Pekkola (1918) also have called this structure the parabasal. 



We have found no evidence that the parabasal of flagellates is 

 a motor or contractile organ and have elsewhere (Kofoid, 1916) 

 advanced the interpretation that it is a reserve body connected with 

 metabolism consequent upon the motor functions of the neuromotor 

 system. While its changes in shape in Chilomastix are far more 

 noticeable than those of the parastyle, this might well be due to the 

 intense activity of the adjacent eytostomie flagellum and of the peri- 

 stomal fiber and parastyle, rather than to its own intrinsic movement. 



In one point our findings are at variance with those of Chalmers 

 aud Pekkola (1918), namely, the origin of the parabasal. They state 

 (p. 225) that it arises from the second or anterior chromatic particle, 

 our secondary blepharoplast. We find that in every case where it is 

 possible to separate the anterior and posterior right blepharoplasts 

 the parabasal is joined to the posterior one only, that is to the right 

 posterior or tertiary blepharoplast. 



The parastyle (fig. A, parast.) is a slender, straight, or slightly 

 curved rod, much smaller and usually more decolorized than the 

 parabasal. It originates from the secondary blepharoplast, and runs 

 posteriorl.y in the left wall of the oral pouch, almost to the posterior 

 end of that cavity, sometimes overlapping the recurved end of the 

 parabasal and more or less obscured by the peristomal fiber above it. 



The relative shapes of parastyle and parabasal, as seen in a series 

 of free flagellates and cysts, are instructive as to their relative func- 

 tions. While the parabasal exhibits a great variety of shapes showing 

 the contractility and mobility of the region in which it lies, the para- 

 style is straighter, has much slighter curvature, and its shapes likewise 

 appear to be correlated with the state of contraction of the cytostome, 

 as though it were passively moved by the activity of that region. 

 There is lack of evidence that it is an active motor organ. It appears 



