6 University of California Publications in Zoology [Vol. 16 



other flagellates is very uncertain. In a few instances there is a dis- 

 tinct rhizoplast in addition to the "axostyle" connecting the "kine- 

 tonucleus" with the nucleus (pi. 38, fig. 58b) ; in the larger number of 

 these long flagellates, however, there is only one line. In this case there 

 is a possible fusion of the rhizoplast and "axostyle" as far as the 

 nucleus and the axostyle extends thence from the nucleus to the 

 posterior end of the body. Occasionally there are other lines (text 

 fig. A; pi. 2, figs. 52, 54), possibly myonemic fibers in the periplast of 

 the body, which show distinctly in iron haematoxylin preparations. 

 These lines are connected directly with the flagellum (pi. 2, fig-s. 

 52, 55). 



The flagellum extends forwards as a single heavy line from the 

 basal granule along the anterior projection of protoplasm for about 

 one-half of its length in the flagellates of the vegetative pha.se (pi. 3, 

 figs. 57-62). This flagellum is readily stained with Giemsa and iron 

 haematoxylin. 



The flagellum is in the margin of the undulating membrane, which 

 shows no specialized structure in the elongate flagellates found in the 

 rectum. It is merely a prolongation of the protoplasm and plays a 

 very small part in the movement of the organism. 



III. MOVEMENT 

 The characteristic, vigorous movement of the elongate flagellates 

 indicates at once their presence in any living material. There are 

 flashes of indistinct forms and a big disturbance of the cellular debris 

 in the field. When the flagellates become more quiet it is observed 

 that the flagellum, body, and undulating membrane all assist in pro- 

 gression. There is a very rapid vibration of the rigid body from side 

 to side, combined with the spiral movements of the flagellate end of 

 the body either to the right or to the left. Then an instant follows 

 in which the spiral movement alone is in evidence. An instant later 

 the flagellate end whips around and the organism darts off in another 

 direction. In comparison with Crithidia gerridis and several other 

 species, Crithidia leptocoridis has a very rigid body. This rigidity is 

 noticeable in the movements. On several occasions, an intestinal 

 preparation of living material showed the rigid flagellates which had 

 escaped from the colon in the act of boring their way into the Mal- 

 pighian tubules at certain points. Many had penetrated at least one- 

 third of the body-length. By careful focusing it was determined that 

 the parasites had actually bored their way thus far. 



