414 THE INFUSORIA 



shoe-shaped, or strap-shaped body. The micronucleus is, in the resting 

 condition, extremely minute and difficult to observe. 

 Only one micronucleus is usually present in each indi- 

 vidual. 



The order PERITRICHA is divided into the following 

 families : 



Family SPIROCHONINA, Stein. Spirochona, Stein. 

 _ (Fig. 22.) Attached to the gills of Gammarusby a sucker. 



PIG 75 Mouth surrounded by a delicate spiral membrane, the 



Nematocysts of inner surface of which is partially provided with ex- 

 Epistyiis umbel- tremely minute cilia. Reproduction DV external eem- 



laria. a, with the . ' , . ", 



thread at rest ; b, mation. Meganucleus oval or spherical, with a clear 

 discharged '(After zone con taining in the resting state a single chromatin 

 Greef.) Each cap- body the nucleolus (?). One to three micronuclei. 0'12. 

 fn 1 ieDgth b Ut Klt Gills of Gammarus. Kentrochona, Rompel (Fig. 3). Adoral 

 membrane in the form of a large wide-mouthed funnel, 

 not spirally twisted. This is supported by four columnar thickenings 

 which project as spines from the margin of the funnel. Meganucleus 

 spherical. 3-4 micronuclei. O04. On the limbs of Nebalia. Kentro- 

 chonopsis, Doflein. With multiple endogenous gemination. Six micro- 

 nuclei. Gills of Nebalia geoffroyi. Chilodocona, Wallengren. Maxillae 

 and maxillipedes of Ebalia and Portunus. 



Family LICNOPHORINA, Biitschli. Spiral girdle scaiotrichous and 

 ciliated. Licnophora, Clap. Aboral sucker surrounded by a circle of cilia. 

 O'l 2. Attached to several marine Invertebrata such as Medusae, Pelecy- 

 poda, Polychaeta, etc. 



Family VORTICELLINA, Biitschli. Trichodina, Stein. Cylindrical in 

 form, with an adhesive disc surrounded by a ring of cilia. O'l. Found 

 on the surface of Hydra, Sponges, Planarians, and other freshwater 

 animals ; and also occasionally in the bladder of Frogs, Newts, and 

 Fishes. Cydochaeta, Jackson. With a ring of very long bristle -like 

 processes just above the ring of cilia of the adhesive disc. O'l. On 

 Spongilla, on the gills of Scorpaena, Trigla, and Serpula, and on the 

 surface of Asteriscus and Ophiothrix. Trichodinopsis, Clap, and L. A 

 remarkable form, with a very much constricted oral extremity, causing 

 the body to assume a conical shape. The whole surface of the body 

 between the oral and aboral rings of cilia covered with long cilia. O'l 3. 

 Parasitic in the gut and lung of Cyclostoma. Scypliidia, Lachmann. 

 Cylindrical forms without a stalk and without an aboral ring of cilia. 

 O'l 2. Attached by the aboral sucker to the skin of freshwater and 

 marine Mollnsca. Gerda, Clap, and L. Cylindrical in form, with the 

 oral region considerably constricted. Very contractile. When swimming, 

 a ring of cilia is formed at the aboral end. 0'2. Freshwater. Hastatella, 

 Erlanger. With long spinous processes. Stagnant freshwater. Astylozoon, 

 Engelmann. Free, with a pointed posterior extremity provided with 

 two or three saltatory bristles. O'l. Freshwater. Vorticelta, Linnaeus, 

 1767, emend. Ehrb., 1838. (Figs. 76 and 77.) This genus is now con- 

 fined to those Vorticellids with a simple unbranched contractile stalk. 

 A large number of species have been described, but as there is great 



