228 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



Morphological trademarks are relatively few. Flagellar garnish- 

 ment is certainly one of these, and the possession (but not the 

 lack) of the ochromonad type of pantoneme flagellum seems to 

 be a reliable symptom of kinship. In the phytomonads, the 

 occurrence of mastigonemes is sporadic and inconsistent with any 

 other suspected index of relationship. Studies of chloroplast and 

 pyrenoid structure, as these become more numerous and precise, 

 will undoubtedly yield additional exciting clues when combined 

 with chemical analysis of photosynthetic pigments and products. 

 The stigma-flagellum coaptation is another character that bears 

 watching. It has been described in chrysomonads and brown-algal 

 zoospores and in euglenids, but not yet in any phytomonad. 



But the majority of phy toflagellates has not indulged, on a large 

 scale, in morphologic experimentation, which means simply that 

 the very different things they do are done differently at a molecular 

 level still beyond our powers of direct visualization. 



The euglenoids are quite another kettle of fish. In them are 

 found for the first time fairly elaborate cytoplasmic constructions 

 that are not in the common cellular repertoire. They have well- 

 developed systems of tubular fibrils underlying the pellicle and 

 (perhaps different kinds) composing the pharyngeal rodorgan in 

 Peranema. The tubular fibril is probably not original with them. 

 Spermatozoids of three land plants {Sphagnum — Manton, 1957a; 

 Vteridium — Manton, 1959c; Marchantia — Heitz, 1959) contain 

 orderly bands of tubular fibrils. Thus it would not be surprising 

 to discover this type of fibril at least in the phytomonads. But 

 apparently it remained to the euglenoids, among phytoflagellates, 

 to discover just how useful it could be. 



Several points of resemblance between the bodonids-trypano- 

 somids and the euglenoids have been noted on p. 143. The 

 most conspicuous is the system of pellicular fibrils connecting 

 with the kinetosomes. In neither group have banded intracellular 

 fibrils been found. Although the bodonid's single Golgi apparatus 

 occupies a position near the kinetosomes (as in chrysomonads and 

 phytomonads, but not in the euglenoids with their numerous 

 dictyosomes), no rhizoplast-like fibrils have been reported as yet. 

 It would be unwise to overemphasize this point, as flagellar 

 rootlets in the phytomonads do not always appear banded, and 



