PLAGIODISCUS. 



[ 604 ] 



PLANARIOLA. 



plants of the family, its stems growing from 

 > to 5" long. 



BIBL. Hook. Br. Ft. ii. Fl - 585 - 

 pt. 1, 111; Br. Jung. 

 pis. 13, 14 ; Ekart, Sijn- 

 ops. Jung. 6 et seq. pi. 1 ; 

 Endlicher, Gen. Plant. 

 Supp. 1, No. 473. 



PLAGIODIS'CUS,Gr. 

 A genus of Diatoma- 

 ceae. Allied to Surirella, 

 but the costae radiating 

 at the ends. 2 species ; 

 valves reniform ; Hondu- 

 ras. (Grunow, M. M. Jn. 

 xviii. 172, figs.) 



PLAGIOG'NATHA, 

 Duj. A genus of Rota- 

 toria containing species 

 included by Ehrenberg 

 in the genera Notommata, Diylena, and 

 Distemma,', distinguished by the arched 

 back and peculiar jaws. 



BIBL. Duj. Inf. 651; Pritchard, Inf. 

 692. 



PLAGIOGRAM'MA. Grev. A genus 

 of Diatomaceaj, family Fragilariae. 



Char. Frustules quadrangular, united into 

 a short fascia; valves with two or more 

 strong, pervious transverse costae, and mo- 

 niliform generally interrupted strise. 



BIBL. Greville, Mic. Tr. 1865, 1866; 

 Rabenh. Fl.Eur..Alg. i. 117; Pritchard, 

 Infm. 773. 



PLAGIOPH'RYS, Clap.-A genus of 

 Actinophryina (Rhizopoda). 



Char. No carapace, pseudopodia nume- 

 rous, arising from one point of the surface 

 of the body. 2 species; freshwater. P. cy- 

 Imdrica (PI. 52. tig. 17). 



BIBL. Clap, et Lach. In/us. 453 ; Archer, 

 Qu. Mic. Jn. 1871, 146. 



PLAGIOPO'GON, St. A genus of Ho- 

 lotrichous Infusoria. Free, oval, longitudi- 

 nally furrowed, oral setae rigid. P. coleps ; 

 length 1-300' '. (Kent, Inf. 508.) 



PL AGIOP'YLA, Stein. A genus of Ho- 

 lotrichous Infusoria. Ovate ; mouth ven- 

 tral, with an undulating membrane ; sur- 

 face with trichocysts. 3 species j fresh and 

 salt water. (Kent, Inf. 538.) 



PLAGIOT'OMA, Duj. A genus of Bur- 

 sarina (Infusoria ciliata). 



Parasitic ; in the intestines and their walls 

 of Vertebrata and Invertebrata, and in the 

 mucus of Mollusca. 7 species. P. lumbrici, 

 in the earthworm ; P. coli, in the human in- 

 testine. 



BIBL. Duj. Inf. 504; Clap, et Lach. 

 Infm. 235. 



PLAGIOT'RICHA, Kt. A genus of 

 Hypotrichous Infusoria : allied to Oxytriclta. 

 2 species ; freshwater. ' ( Kent, Inf. '771.) 



PLAGIOT'ROPIS, O'Meara. A genus 

 of Diatomacese closely allied to Amphi- 

 prora, Ehr. 



BIBL. O'Meara, Qu. Mic. Jn. 1874, 88. 



PLANA'RIA, Mull. A genus of Annu- 

 loida, of the order Turbellaria, and sub- 

 order Planarida. 



Char. Body soft, flattened, oblong or 

 oval, not jointed, covered with vibratile 

 cilia ; neither suckers, bristles, nor leg-like 

 appendages present. 



Some parts of the structure of these ani- 

 mals have been noticed under ANNULATA 

 in speaking of the Turbellaria. The mouth 

 is situated on the under surface of the 

 middle of the body, at the end of a retrac- 

 tile proboscis ; there is no anus ; the mouth 

 leads to a capacious stomach , giving off 

 dendritically-branched caeca, somewhat as 

 in one joint of a Tcmia (PI. 21. fig. 14). 

 Their motion is continuous and gliding, 

 upon water-plants, or the sides of glass jars. 

 The anterior part of the body exhibits a 

 curved row or a single pair of eyes, and 

 sometimes ear-like projections. They mul- 

 tiply by division, and the formation of ova, 

 which are enclosed in a coloured capsule. 



Some of the species are very common in 

 pools, and resemble, at first sight, minute 

 leeches. P. niyra, which is black, has a 

 row of marginal anterior eyes, and two 

 lateral and one mesial projection; length 

 about 1-2". P. bi-unnea, dusky-brown, with 

 a dark mesial line ; eyes as above ; length 

 rather less. P. lactea, cream-coloured, 

 tinged with pale reddish brown, truncate in 

 front, -with two slight lateral auricles ; eyes 

 two or four ; length 1-2 to 3-4". P. torva, 

 grey or black ; obtuse in front, angles 

 rounded, centre projecting; eyes two, with 

 a white halo ; length 1-2". Of the other 

 species some are marine. 



BIBL. Johnston, Non-parasitical Worms ; 

 Duges, Ann. Sc. Nat. 2. xv. and xxi. j 

 CErsted, System, d. Plattiviirmer ; Diesing, 

 Helminth. ; Daly ell, Powers of Creation, ii. ; 

 Schultze, Naturg. Turbett. ; Huxley, Comp. 

 An. ; Vaillant, Mn. Mic. Jn. i. 311 ; R. 

 Lankester, Pop. Sc. Rev. 1867, vi. 388; 

 Moseley, Phil. Trans. 1877, xvii. 105. 



PLANARI'OLA, Duj. A doubtful ge- 

 nus of Infusoria. 



P. rubra (PI. 31. fig. 65). Aquatic, in 



