704 



PROTOZOOLOGY 



D. nasutum (Miiller) (Figs. 21, e, f; 40; 75; 91; 300, e-g). 80-200m 

 long; endoplasm highly granulated; with two girdles of pectinelles; 

 feeds on Paramecium ; spherical cysts (Fig. 75) with three walls, 60- 

 80 /x in diameter; fresh water. Morphology (Thon, 1905; Calkins, 

 1915; Beers, 1935); encystment, food requirement and conjugation 

 (Beers, 1927, 1930, 1933, 1935); longevity of cysts (Beers, 1937); 



Fig. 300. a, Teuthophrys trisula, X330 (Wenrich); b, Metacystis trun- 

 cata, X270 (Cohn); c, Vasicola ciliata, X250 (Kahl); d, Pelatr actus 

 grandis, X170 (Penard); e-g, Didinium nasutum, X170 (Kudo); h, D. 

 balbianii, X290 (Butschli) ; i-k, Mesodinium pulex (i, X670; j, oral view; 

 k, oral tentacles, X1330) (Noland); 1, m, M. acarus (1, X670; m, oral 

 tentacles, X1330) (Noland); n, Askenasia faurei, X530 (Faur^-Fremiet); 

 o, Cyclotrichium meunieri, X780 (Powers). 



