112 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



was briefly examined in thin section by Wolken and Palade in 

 1953. Although the high quality of the single micrograph 

 published was notable for that early date, it does not reveal any 

 morphological features peculiar to the genus. The chloroplasts 

 have rather uniformly parallel lamellae and flank the anterior 

 nucleus. Neither rhizoplast nor Golgi bodies were noted by the 

 authors. In an unidentified solitary ochromonad, possibly 

 Ochromonas, occurring as a contaminant in a bacterized ciliate 

 culture studied by Pitelka (unpublished), Golgi elements were 

 seen in a constant position anterior to the nucleus and obliquely 

 posterior to the two flagellar basal bodies, but observations were 

 too few to justify any conclusions regarding the presence or 

 absence of a rhizoplast. The chloroplasts in this organism appeared 

 exceptionally small, and the posterior cytoplasm was filled with 

 vacuoles containing bacteria or their partially disintegrated 

 remains. 



A brief study of whole mounts of the species Stokesiella 

 dissimilis (Petersen and Hansen, 1960b) should be mentioned here. 

 The genus often is placed among the lower zooflagellates (see 

 Bicoecida, p. 136), but Hollande (1952a) recognizes it as a member 

 of the family Ochromonadidae. Like many chrysomonads, the 

 organism dwells within an open sheath or envelope produced by 

 the cell. In Petersen and Hansen's figures only the longer 

 flagellum was visible emerging from the envelope, and this was 

 clearly of the ochromonad pantoneme type. The delicate, cup- 

 shaped envelope consisted of a single band of striated membranous 

 material, wound in a tight spiral with thickenings at its over- 

 lapping edges. 



Chrysochromulina is one of a group of genera considered to be 

 triflagellate. One of the most interesting results of Parke, Manton, 

 and Clarke's series (1955-59) of studies of eight new species 

 referred to this genus was the discovery that the third appendage 

 is not a flagellum but a slender retractile filament with an adhesive 

 tip, named the haptonema. In some species it may be extended 

 to several times the length of the flagella and in all it evidently is 

 used for temporary fixation to a substrate. It may be tightly 

 coiled or fully extended during active swimming but it does not 

 function as a locomotor organelle. For the first species described 



