278 BIOLOaV OF THE PROTOZOA 



braiies are formed consisting of alternate cellulose walls and gela- 

 tinous substance (Gloeodiniii)ii), while Sti/Iocliniiini possesses a gela- 

 tinous stalk. Swarmer stages are entirely unknown. 



Sub-order 2. Adinina, Bergh. 



These very interesting forms possess two flagella but no furrows. 

 The body is enclosed in a bivalved shell composed of a substance 

 similar to cellulose. The right and left valves come together in a 

 median sagittal suture as in the Dinophysidse but interlocking teeth 

 are absent. An aperture between the valves at the anterior end 

 serves as an outlet for the flagella, one of which extends freely in 

 the water while the second, corresponding to the annular flagellum 

 of other Dinoflagellida, after emerging from the shell, bends sharply 

 and vibrates in a circle around the base of the first flagellum (Fig. 

 129, B). This condition is foreshadowed in the genus Amphidinium 

 where the epitheca is a mere knob (Fig. 70, p. 130). In Proro- 

 centrum the anterior spine-like horn ma\' represent the reminiscence 

 of such a modified epitheca (Fig. 129, .1). In E.rnviceUa even this 

 remnant is absent. 



The yellow chromatophores are band-form and usually two in 

 number enclosing pyrenoids. Division is said to take place in the 

 sagittal plane, each daughter cell retaining one of the parent valves 

 and regenerating a second. The typical genera are I^rorocentnnii, 

 Haplodiniiim, and ExuvioeUa. 



Sub-order 3. Cystoflagellina, Haeckel. 



The systematic position of the two genera Leptodiscus and 

 Craspedotella wdiich are usually included in the Cystoflagellida, is 

 not yet clearly established. Noctiluca, formerly the type genus of 

 the group, is now definitely recognized as a dinoflagellate. Stein, 

 on the basis of structure of the swarm spores, early recognized the 

 possible relationship but Biitschli, followed by the majority of later 

 writers, regarded it as sufficientl\' distinct to justify its inclusion 

 in an independent group. Kofoid (1920) has given further evidence 

 of its Dinoflagellate affinities. 



Noctiluca is spherical, gelatinous in consistency, and from 1 to 

 1^ mm. in diameter. The protoplasm is massed at one pole with 

 strands passing to the periphery in all directions giving a plant-like 

 or parenchymatous appearance to the cell. Shell and furrow 

 characteristic of the Dinoflagellates are entirely absent. A peculiar, 

 external, "peristomial" apparatus lies above the denser proto- 

 plasmic mass. This consists of a collar-like protuberance from 

 the floor of which a minute flagellum, a cross-striped powerful ten- 

 tacle, and a curious roughened structure called the "tooth" arise. 



