PHYTOMASTIGINA 



55 



Oodinium (Fig. 34). Thin-cuticled ; pear-shaped; colourless; living 

 as an ectoparasite on marine pelagic animals, and possessing the 

 typical dinoflagellate organization only in the spore stage. 



Dinamoehidium. Colourless and holozoic; completely Amoeba-like 

 in the ordinary phase, but forming dinoflagellate swarm spores in a 

 fusiform cyst. 



Noctiluca (Fig. 41). (Formerly placed in an independent order — 

 Cystoflagellata.) Large, peach-shaped forms; colourless and holo- 

 zoic; with highly vacuolated protoplasm; a stout pellicle; and, in 



nil. 



tr.fl.- 



t^-ann. 



ntc.--i 



Fig. 40. Dinoflagellata. A, Ceratium macroceras, x about 300. B, Polykrikos 

 schwarzi, x 250. C, A discharged "nematocyst" of Po/j'/en'i^o^. After various 

 authors, with modifications, ann. annuli; cph. chromatophore ; cu. cuticle; 

 In.fl. longitudinal flagellum; ntc. "nematocyst" ; nu. nucleus; sul. sulcus; 

 sut. suture between plates of cuticle ; tr.fl. transverse flagellum. 



the groove of the peach, an elongate mouth, a small flagellum, a 

 structure known as the tooth which is said to represent the transverse 

 flagellum, and a strong tentacle, homologous with a similar structure 

 in certain more normal dinoflagellates. Noctiluca is phosphorescent. 

 Like other dinoflagellates it reproduces by binary fission and by spore 

 formation after multiple fission. The spores are more dinoflagellate- 

 like than the adult. Marine, pelagic. 



Dinothrix. Normally in the palmella phase, forming thread-like 

 growths. Marine. 



