100 ] The Classification of Lower Organisms 



1. Not as above, always without photosynthetic 

 pigments. 



2. Amoeboid Family 3. Dinamoebidina. 



2. Flagellate or free-floating. 



3. With multiplied girdles, without 

 tentacles or specialized light-sensi- 

 tive organelles Family 4. PoLYKRiKroA. 



3. With one girdle or none. 



4. Cells more or less isodiamet- 

 ric. 



5. With prominent light-sen- 

 sitive organelles, some- 

 times with tentacles Family 5. Pouchetiida. 



5. Without light-sensitive or- 

 ganelles, with tentacles. 

 6. Not exceptionally 



large Family 6. Protodiniferida. 



6. Reaching exceptional 

 sizes, to 1 mm. in di- 

 ameter Family 7. Noctilucida. 



4. Cells dome-shaped Family 8. Lepodiscida. 



2. Parasitic Family 9. Blastodinida. 



Family 1 . Phytodiniacea [Phytodiniaceae] Schilling in Pascher Siisswasserfl. 

 Deutschland 3: 61 (1913). Family Phytodinidae Calkins Biol. Prot. 277 (1926). 

 Dinocapsales, Dinocapsaceae, Dinococcales, Dinotrichales, and Dinotrichaceae 

 Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Orders Dinocapsales, Dino- 

 coccales, and Dinotrichales, and families Gloeodiniaceae, Hypnodiniaceae, Dino- 

 trichaceae, and Dinocloniaceae Pascher in Beih. bot. Centralbl. 48, Abt. 2: 326 

 (1931). Organisms with numerous yellow to brown plastids, walled and non-motile 

 in the vegetative condition, reproducing by gymnodinioid zoospores. Some fifty 

 species are known; it is only recently that Thompson (1949) has found several of 

 these in America. Cells multiplying in a gelatinous matrix: Gloeodinium. Cells 

 solitary, dividing into several which escape usually in the flagellate condition; with 

 smooth ellipsoid walls: Phytodinium, Stylodinium; anvil-shaped, stalked and with 

 two horns: Racihorskya; tetrahedral, with horns at each comer: Tetradinium; with 

 a ring of about six horns: Dinastridium. Tending to produce filaments; marine: 

 Dinothrix, Dinoclonium. 



Family 2. Gymnodiniacea [Gymnodiniaceae] Schiitt in Engler and Prantl Nat. 

 Pflanzenfam. I Teil, Abt. lb: 2 (1896). Subfamily Gymnodinida Bergh in Morph. 

 Jahrb. 7: 274 (1882). Gymnodinidae Kofoid in Bull. Mus. Comp. Zool. Harvard 

 50: 164 (1907). Family Gymnodiniidae Poche in Arch. Prot. 30: 162 (1913). The 

 typical unarmored dinoflagellates, free-swimming, with sulcus and girdle, without 

 tentacles or a conspicuous light-sensitive organelle, commonly with photosynthetic 

 pigments. 



The genus which is most numerous in species is Gymnodinium Stein. It includes 

 both pigmented and non-pigmcnted species, mostly marine, occasional in fresh water, 

 the girdles nearly equatorial and forming nearly complete circles. The cells readily 

 become encysted, and the cysts may grow to large sizes, reaching diameters of 0.5 mm. 

 These cysts have been taken for a distinct genus Pyrocystis. Observed in darkness, 



