ZOOFLAGELLATES 159 



Chapter 2, but their orderliness can only be appreciated by 

 reference to the original work. Flagellar morphology is essentially 

 similar in Trichonympha, Pseudotrichonympha, and Holomastigotoides. 

 In the first two genera, a cartwheel structure consisting of a central 

 cylinder and radiating spokes occupies the proximal half of the 

 kinetosomes. In Trichonympha the distal portion of the kinetosome 

 is empty but in Pseudotrichonympha it contains a cluster of three 

 delicate cylinders in kinetosomes on some parts of the body and a 

 mass of dense granules in others. In Holomastigotoides the whole 

 kinetosome appears empty. Very sinuous fibrous ribbons lie 

 close to the postrostral basal bodies in Pseudotrichonympha, 

 somewhat like the parabasal filaments of Trichonympha. In 

 Holomastigotoides a regularly undulating ribbon of fine filaments 

 with periodic transverse densities makes intimate connection 

 with the kinetosomes in each spiral row near the posterior end 

 of the body. Anteriorly, a thick, homogeneous band lies next 

 to the basal bodies; nearby run ribbons of tubular fibrils that 

 Gibbons and Grimstone identify as axostylar fibers. 



Grimstone's (1959c) observations on the cytoplasmic and 

 nuclear membranes of Trichonympha have also been summarized 

 in Chapter 2. His picture of the parabasal fibrils shows that the 

 repeating period, 36 to 54m/x in length, contains secondary bands 

 within it. Publication of Grimstone's more recent morphological 

 and cytochemical work on Trichonympha will undoubtedly clear 

 up many additional questions left unanswered by the studies of 

 Pitelka and Schooley. One of these is the nature of ovoid, 

 membrane-bounded bodies with very fine canalicular contents 

 provisionally identified by the latter authors as mitochondria. 



Reflecting on the morphology of the flagellar apparatus and 

 associated structures in the flagellates as a whole, one cannot fail 

 to be impressed by the versatility of the cytoplasmic locus 

 morphologically identified by the presence of the kinetosome. 

 At the same time, the repetition of similar patterns in very dis- 

 similar flagellates emphasizes the underlying analogy — and 

 surely homology — of the apparatus wherever it is found. The 

 constancy of flagellar and kinetosomal fibril pattern needs no 

 further comment. Superficial elaborations such as mastigonemes 

 and scales are restricted to the phytoflagellates and have been 

 discussed in the preceding chapter. Accessory structures en- 



