13: 



PROTOZOA 



k 



// 



H 



and fresh -waters. GyninodAnium pulvisculus is sometimes parasitic 

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

 verse grooves, each with its flagellum, 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. Peridinium 

 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 " was published by 

 Schiitt.' 



The Cystoflagellates con- 

 tain only two genera,' Nocti- 

 luca, common at the surface 

 of tranquil seas, to which, 

 as its name implies, it gives 

 phosphorescence, and Zepto- 

 discus, found by E. Hert- 

 wig in the Mediterranean. 

 Nodiluca is enormous for a 

 Flagellate, for with the form of 

 a miniature melon it measures 

 about 1 mm. (ys'O 0^ more in 

 diameter. In the depression- 

 is the "oral cleft," from one 

 end of which rises, by a broad base, a large coarse flagellum,. 

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

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



ElG. 47. — Pyrocystis fusifonnis, Murray. 

 X 100. From the surface in the Guinea 

 Current. (From Wyville Thomson.) 



^ According to Bergh, Polylcrilcos has as many nuclei as grooves, each accompanied 

 by one or more "micronuclei." Possibly these latter bodies are merely blepharoplasts, 

 in connexion with the transverse flagella. 



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



' The luminous genus, Pyrocystis (Fig. 47), regarded as a Cystofiagellate by 

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

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



