Ciliophora 345 



The family includes two genera: Coleps Nitzsch (74, 99, 100, 157; Fig. 7. 4, B, G-I) and 

 Tiarina Bergh (100; Fig. 7. 4, A). 



Family 7. Didiniidae. These ciliates are radially symmetrical with re- 

 spect to the longitudinal axis. The anterior cytostome (Fig. 7. 5, B, F) is 

 not surrounded by cilia although there is a ring of circumoral tentacles 

 in Mesodiy-iiiim. A circlet of pectinellae (slender membranelles) usually 

 lies at or near the rim of the anterior pole (Fig. 7. 5, C, E, G), and there 

 may be one to several similar rings of pectinellae located more posteriorly. 

 The rest of the body may be either naked or ciliated in different species. 

 A band of circumpharyngeal trichites is characteristic. Although a few 

 species apparently eat algae, a carnivorous diet is the usual one. Didiiiium 

 nasutum is noted for its habit of capturing and ingesting such ciliates as 

 Paraynecium (150). 



The family includes the following genera: Askenasia Blochmann (100, 165; Fig. 7. 

 5, F, G), Cyclotrichiuw Meunier (100, 171; Fig. 7. 5, H), Didinium Stein (97, 100; Fig. 

 7. 5, C-E), and Mesodiniuin Stein (100, 158; Fig. 7. 5, A, B). Mnnodiniiitu Fabre- 

 Domergue (58), with one anterior ring of pectinellae. has been considered a separate 

 genus by some workers; others include such ciliates in Didinium Stein. The family 

 includes both fresh-water and marine species, and Cyclotricliiurn rneunieri has been 

 recorded as a cause of red water in the Gidf of Maine (171). 



Family 8. Dysteriidae. These hypostomes differ from the Chlamydodon- 

 tidae and Nassulidae in the presence of a ventral protoplasmic stylus 

 (Fig. 7. 5, I-K). In Dysteria this structure may adhere to a solid surface 

 and serve as a temporary anchor (46), whereas the stylus in Trochilioides 

 secretes a slender filament which serves the same purpose (64). The dorsal 

 surface is not ciliated and a reduction of the ventral ciliation is often 

 noticeable. A pharyngeal rod-apparatus is characteristic. The Dysteriidae 

 are mainly marine ciliates which feed mostly on diatoms, other algae, or 

 bacteria. 



The family includes five genera: Dysteria Huxley (46, 102; Fig. 7. 5, J), Hartmannula 

 Poche (102; Fig. 7. 5, K), Scaphidion Stem (102), Trochilia Dujardin (102; Fig. 7. 5, 

 I), and Trochilioides Kahl (64, 102). 



Family 9. Holophryidae. These are rather uniformly ciliated species in 

 which the cytostome lies at or near the anterior pole and often opens on 

 a rounded elevation. There is generally a circumpharyngeal zone of 

 trichites (Fig. 7. 6, A), and an adoral row of fused cilia (syncilia) is some- 

 times present (Fig. 7. 6, F). Form of the body ranges from plump ovoid or 

 cylindrical shapes to long slender types, the latter sometimes possessing 

 a very extensible and mobile "neck" several times as long as the rest of 

 the body. Feeding habits vary widely. Some species are rapacious carni- 

 vores, pursuing and capturing other ciliates or rotifers. Some usually eat 

 small flagellates, others feed mainly on bacteria and small algae, while 



