132 



PROTOZOA 



and fresh-waters. Gyvinodinium pulviseulus is sometimes parasitic 

 in Aj)pendindaria (Vol. VII. p. 68). Polykrikos ^ has four trans- 

 verse grooves, each with its Hagellum, besides the terminal one. 



Many of the marine species 

 are phosphorescent, and play 

 a large part in the luminosity 

 of the sea, and some give it 

 a red colour. 



Several fossil forms have 

 been described. Peridiniuvi 

 is certainly found fossil in 

 the firestone of Delitzet, be- 

 longing to the Cretaceous. A 

 full monograph of the group 

 under the name " Peridi- 

 niales " w^as published by 

 Schiitt.- 



The Cystoflagellates con- 

 tain only two genera,^ Kocti- 

 luca, common at the surface 

 of tranquil seas, to which, 

 as its name implies, it gives 

 phosphorescence, and Lepto- 

 discus, found by K. Hert- 

 wig in the Mediterranean. 

 Noctiluca is enormous for a 

 Flagellate, for with the form of 

 a miniature melon it measures 



Pyrocystis fusiformis, Murray, about 1 mm. {-^-r'.') Or morC in 



^ ^^' ^'~ t:^.?"^'^ diameter. In" the depression 



is the "oral cleft," from one 

 end of wliich rises, by a broad base, a large coarse iiagellum, 

 as long as the body or longer and transversely striated. In 

 front of the base of the flagellum are two lip-like promin- 



X 100. Prom the surfn 

 Current. (From Wyville Thomson.) 



1 According to Bergh, Polykrikos has as many nuclei as grooves, each accompanied 

 by one or more "niicronnclei." Possibly these latter bodies are merely blepliaroplasts, 

 in connexion with the transverse flagella. 



2 Engler and Prantl's PJlanzenfamilicn, 1. Teil, Abt. 1, 1896. 



» The luminous genus, Pyroeijstis (Fig. 47), regarded as a Cystoflagellate by 

 Wyville Thomson, has a cellulose wall, no mouth, and in the zoospore state has 

 the two flagella in loncritudinal and transverse grooves of the Dinoflagellata. 



