HOLOTRICHA 501 



Genus Mesodinium Stein. Ovoid; an equatorial furrow divides 

 conical anterior and spherical posterior parts; in the furrow are in- 

 serted 2 (or 1) rings of strong cilia; one directed anteriorly and 

 the other posteriorly; with tentacle-like retractile processes 

 around the cytostome; fresh or salt water. 



M. pulex (Claparede et Lachmann) (Fig. 230, i-k). Oral ten- 

 tacles with trifurcate tips; body 20-3 l/x long; salt water; Florida. 

 Noland states that the freshwater forms are 21-38^ long. 



M. acarus Stein (Fig. 230, I, m). Oral tentacles with capitate 

 tips; 10-16/i long; salt water, Florida (Noland). 



Genus Askenasia Bloohmann. Resembles Didinium; ovoid; 

 with 2 closely arranged rings of long cilia; anterior ring made up 

 of some 60 pectinelles which are directed anteriorly; posterior 

 ring composed of about the same number of membranellae or 

 cirri, directed posteriorly and arranged parallel to body surface; 

 fresh or salt water. 



A. volvox (Claparede et Lachmann) (Fig. 230, n). Body oval, 

 posterior end broadly rounded; anterior region conical ; pectinelles 

 about 13^ long; below the second ring of cirri are found long 

 (40/x) bristles; a spherical macronucleus with a micronucleus; 

 body about 50-60m long; fresh water. 



Genus Cyclotrichium Meunier. Body spheroid to ellipsoid with 

 a large non-ciliated oral field which is surrounded by a pectinelle- 

 ring, the remaining part naked or slightly ciliated; macronucleus 

 sausage-form; cytopharynx not recognized; endoplasm highly 

 vacuolated; in marine plankton. 



C. meunieri Powers (Fig. 230, o). Anterior end broadly rounded; 

 posterior region conical; cytostome obscure; oral funnel at ante- 

 rior end in a depression; broad ciliated band at about middle; 

 ectoplasm with concave chromatophore (haematochrome) plates 

 on surface, below which numerous pyrenoids occur in vacuoles; 

 endoplasm with numerous granules; 25-42^1 by 18-34/x; Powers 

 (1932) found that the 'red water' in Frenchman Bay in Maine 

 was caused by the swarming of this organism. 



Family 4 Colepidae Claparede et Lachmann 



Genus Coleps Nitzsch. Body-form constant, barrel-shaped; 

 with regularly arranged ectoplasmic plates; cytostome at ante- 

 rior end, surrounded by slightly longer ciha; often spinous pro- 

 jections at or near posterior end; 1 or more caudal cilia, often 

 overlooked; fresh or salt water. Many species. 



