110 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



opposite the point of origin of the rhizoplast, is a second kineto- 

 some, perpendicular to the primary one and parallel to the cell 

 surface. From its apex, a very short (about 1 p) flagellum extends 

 into a tubular invagination of the cell surface. This second 

 flagellum, lying in its pit and thus surrounded throughout its 

 length by a flagellar membrane and by the invaginated cell 

 membrane, occupies the concavity of the stigma. The flagellum 

 contains the usual 11 fibrils in an unusually dense and expanded 

 matrix, so that the whole organelle is spindle-shaped. 



Rouiller and Faure-Fremiet refer to the two kinetosomes and 

 their associated structures as the kineto-rhizoplastic complex and 

 the kineto-stigmatic complex. Both complexes occur in other 

 flagellates. The kineto-stigmatic complex has been discussed in 

 Chapter 2. 



In a brief report illustrated only by a diagram of a non-flagellated 

 cell, Hovasse and Joyon (1957) describe the ultrastructure of a 

 colonial chromulinid, Hydrurus foetidus. Cells of this species 

 secrete a tough gelatinous substance that binds the division 

 products together until long, multibranched palmelloid colonies 

 are formed. Recently divided cells may transform into supposedly 

 uniflagellated swimmers and leave the colony. The non-flagellated 

 colonial cell, according to Hovasse and Joyon, shows clear 

 polarity. The nucleus, Golgi zone, and leucosin droplets are 

 found in the anterior part of the cell, the large chloroplast 

 posterior to these, with microtubular mitochondria scattered 

 throughout. Many clear, small, vesicles under the cell surface 

 probably are mucigenic bodies that secrete the palmella jelly. No 

 kinetosome is indicated in the diagram and the authors do not 

 comment on the process of flagellum production. They refer to 

 a single flagellum in the swimming cell, and remark that the Golgi 

 apparatus is more distinctly oriented in the flagellate than in the 

 palmelloid state. 



Although Ochromonas and related small species of the biflagellate 

 family Ochromonadidae are cultured in chemically defined media 

 and available in laboratories everywhere, no electron-microscope 

 studies of the type genus have yet been published. Two other 

 ochromonads, Synura caroliniana (Manton, 1955a) and Para- 

 physomonas vestita (Manton and Leedale, 1961c) have been studied 

 in detail with the electron microscope. The spherical colonies of 



