380 Ihiiversity of California Publications in Zoology [Vol.20 



connect the centrosome with the central karyosome as it sometimes 

 does in other flagellates, such as Giardia (Kofoid and Swezy, 1922). 



The undulating membrane (und. memb., fig. A) extends from the 

 primary blepharoplast posteriorly in a slightly leiotropic spiral (pi. 

 37, fig. 4) of not over 0.5 turn at the most and extending posteriorly 

 about 0.8 of the length of the body to the end of the parabasal body, 

 where it terminates with the emergence of the marginal filament as 

 the posterior free flagellum. The number of undulations present in 

 this membrane at any one time appears to be a function of their 

 rate of progress. They are not always evident in fixed material. 

 In active free flagellates they move so rapidly as to defy estimation. 

 In fixed material one finds at the most (pi. 37, figs. 1, 7) eight to ten 

 undulations. 



The membrane consists of the marginal filament {marg. fil., fig. A) 

 which is morphologically a flagellum originating from the primary 

 blepharoplast, enclosed within the outer pellicle, and terminating 

 distally in a free flagellum (post. fr. flag., fig. A) which is about 0.5 

 of the length of the bodj- or more. It also contains a ribbon-like 

 extension of the periphery of the bodj^ at whose base runs the para- 

 basal body {par. b., fig. A). This structure is a curved rod of uniform 

 caliber and regular course, originating from the primary blepharo- 

 plast and following the course of the undulating membrane. It 

 terminates at the point of emergence of the posterior free flagellum. 

 It stains lightly and destains very readily in our material and is 

 often located with difficulty, if at all. 



The axostyle {ax., fig. A) is a stout rod of hyaline appearance 

 and uniform caliber, which appears to originate from the primary 

 blepharoplast and to extend posteriorly in an axial position. Its 

 posterior end projects bej'ond the cytoplasm as a rather bluntly 

 pointed tip for varying distances, depending upon the amount of 

 cytoplasm present and upon the degree of contraction of the body. 

 Its free end rarely attains a length of 0.5 that of the cytoplasmic 

 body. Its varying degree of curvature in different individuals is 

 suggestive of the contractile function which we have seen and de- 

 scribed in Trichomonas (1915). 



The cytostome {eyt., fig. A) is a well-defined and characteristic 

 structure. It is an elongated, broadly comma-shaped, often slightly 

 protuberant area (pi. 37, figs. 3, 6) on the opposite side of the body 

 from the undiilating membrane. It extends from the anterior tip of 

 the body posteriorly for about 0.35 of the length of the body and 



