PHYTOMONADIDA 115 



phores are present. Asexual reproduction takes place within 

 the shell; the valves may become separated from each other 

 owing to an increase in the gelatinous contents. 



Genus Phacotus Perty. The valves are distinct. Body form 

 circular in front view and lenticular in profile. The proto- 

 plasmic body does not fill the dark-colored shell completely. 

 The flagella protrude through a foramina. Asexual reproduction 

 into 2 to 8 individuals. 



Phacotus lenticularis (Ehrenberg) (Fig. 39, g, h). In stagnant 

 water. Body about 10 to 15 microns in diameter. 



Genus Pteromonas Seligo. The body is broadly winged in 

 the plane of the junction of the two valves. Protoplasmic body 

 fills the shell. The chromatophore is cup-shaped and contains 

 1 to 6 pyrenoids. Asexual reproduction into 2 to 4 individuals. 

 Sexual reproduction by isogamy. Zygotes are usually brown 

 colored. 



Pteromonas angidosa (Carter) (Fig. 39, i). With a rounded 

 wing and four protoplasmic projections in profile. About 16 

 microns in diameter. Fresh water. 



Genus Coccomonas Stein. The envelope is somewhat rect- 

 angular and shows a single opening at the anterior end for the 

 flagella. Inner wall distinct. The protoplasm does not fill the 

 space formed by the envelope. Asexual reproduction into four 

 individuals. 



Coccomonas orbicularis Stein. In ditches and ponds. 



References 



Crow, W. B. 1918 The classification of some colonial chlamy- 



domonads. New Phytologist, Vol. 17. 

 Dangeard, p. 1900 Obsei\'ations sur la structure et le de- 



veloppement du Pandorina moriim. Le Botaniste, T. 7. 

 Entz, G. Jr. 1913 Cytologische Beobachtungen an Polytoma 



uvella. Verb. Deutsch. Zool. Ges. Ver., 23. 

 Janet, C. 1912, 1922, 1923 Le Volvox. I, II and III Memoires. 



Paris. 

 KoFOiD, C. A. 1900 Plankton studies. Nos. 2 and 3. Ann. 



Mag. Nat. Hist., Ser. 7, Vol. 6. 

 Mast, S. O. 1928 Structure and function of the eye-spot in 



unicellular and colonial organisms. Arch. f. Protistenk., 



Vol. 60. 

 Pascher, a. 1927 Volvocales — Phytomonodinae. Siisswasser- 



flora Deutschlands, etc., H.4. 



