HOLOTRICHA 



705 



excystment (Beers, 1945, 1946) (Fig. 75); fibrillar structures (ten 

 Kate, 1927); meiosis in conjugation (p. 206) (Prandtl, 1906). 



D. balbianii (Fab re-Do mergue) (Fig. 300, h). 60-100ju long; a 

 single girdle of pectinelles near anterior end; fresh water. 



Genus Mesodinium Stein. Ovoid; an equatorial furrow marks 

 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 and salt water. 



M. pulex (Claparede and Lachmann) (Fig. 300, i-k). Oral ten- 

 tacles with trifurcate tips; body 20-3 1/x long; salt water; Florida. 

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



M. acarus Stein (Fig. 300, I, m). Oral tentacles with capitate tip; 

 10-16m long; salt water, Florida (Noland, 1937). 



Fig. 301. Cyclotrichium meunieri (Bary and Stuckey). a, diagram of or- 

 ganism in life, X665; b, a composite figure from stained specimens, X 1130 

 (c, cirri; ch, chromatophores; cr, ciliary row; cy, "cytostome"; py, pyre- 

 noid). 



Genus Askenasia Blochmann. 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 long cilia directed posteriorly and 

 arranged parallel to body surface; fresh or salt water. 



A. faurei Kahl (Fig. 300, n). Body oval, anterior end broadly 

 rounded; posterior region conical; pectinelles about 13/x long; the 

 second band (10/z) of long cilia; an ellipsoid macronucleus; a micro- 

 nucleus; body about 58-60^ long; fresh water. 



Genus Cyclotrichium Meunier. Body spheroid to ellipsoid with a 

 large non-ciliated oral field which is surronded by a pectinelle-ring, 



