VARIATIONS IN SHAFT STRUCTURE — FLAGELLA 37 



the flagellar membrane. Internal modifications in the form of 

 spines on the fibrils and connexions between the fibrils and the 

 flagellar membrane have also been found. 



Many light microscopists described *' Flimmergiessel " or 

 flimmer-flagella (Brovs^n, 1945), which are flagella bearing 

 hair-like appendages. Flagella were classified by Deflandre (1934) 

 and Vlk (1938) on the basis of shape and the distribution of hairs. 

 Work with the electron microscope has shown that these append- 

 ages fall into two distinct groups, the thicker *' mastigonemes," 

 which are from about 1 /u, to a few micra long and 100 to 200 A in 

 diameter, and much finer filaments which form a felted zone 

 around the flagellar shaft in some species. Information is very 

 scanty on these fine filaments which have been figured by Pitelka 

 and Schooley (1955), and appear as a zone about 0-2 fx thick 

 around the anterior flagellum of Peranema in electron micrographs 

 taken by Roth (1959) (PL Vllb). Fine filaments of this type 

 have been reported from the flagella of the sponge Microciona by 

 Afzelius (1961b, c), who found filaments about 20 A thick and 0-2 

 to 0*3 ju, long arranged in two rows in the plane of the central 

 fibrils as shown in Plate VI Ic. 



Mastigonemes occur in a single row on the anterior flagellum of 

 euglenid flagellates, and perhaps on the transverse flagellum of 

 dinoflagellates. In the most frequent arrangement there are two 

 rows along opposite sides of the flagellum as on the anterior 

 flagella of spermatozoids and zoospores of brown algae, yellow- 

 green algae, and some fungi, and on flagella of a variety of 

 flagellates (PI. VIII, IX) (Manton, 1956; Pitelka and Schooley, 

 1955). The extent of mastigonemes along the flagellum may vary; 

 a greater or lesser region at the tip of the flagellum may be devoid 

 of flimmer hairs. The flagella of the animal-like flagellates lack 

 mastigonemes as do also the posterior flagella of most biflagellate 

 forms, though these may bear some of the fine filaments. Most 

 mastigonemes have two regions, a stouter basal region ending in 

 one or more fine terminal filaments (PI. Villa), which are usually 

 short but may be as long as the basal part. There is doubt as to 

 the position of attachment of the mastigonemes; Manton (1956) 

 is of the opinion that they are attached to the peripheral fibrils of 

 the shaft, or between a pair of such fibrils, while Pitelka and 

 Schooley (1955) find that in some cases at least the mastigonemes 



