532 ORDER HOLOTRICHA. 



With the Ophryoglenidse commences an important and extensive series of the 

 Holotrichous Ciliata, distinguished in all instances by the possession of a more or 

 less extensively developed membraniform appendage, in addition to the usual com- 

 plement of cuticular and oral cilia. Where such a supplementary membrane is 

 extensively developed, as in the genera Lembus and Proboscella, there can be but little 

 doubt that we have foreshadowed the system of conspicuously larger adoral cilia 

 characteristic of the ordinary Heterotricha, and which system not unfrequently 

 originates as a similar simple band-like membrane. A partial recognition of the 

 natural affinity of the membrane-bearing Holotricha is recorded by Stein in his 

 classification scheme, reproduced at p. 210 of vol. i. He at the same times places 

 the genus_Pafiofl/irys among the ordinary Paramsecina, while all the rest are collected 

 together in the single family group of the Cinetrochilina, without regard to the 

 essentially distinct plans upon which, in so many of these genera, the membraniform 

 appendage is constructed. 



GENUS I. OPHRYOGLENA, Ehrenberg. 



Animalcules free-swimming, persistent in shape, more or less ovate and 

 depressed, having a convex dorsal and flattened ventral surface, the oral 

 fossa opening on the ventral aspect at a little distance from the anterior 

 extremity, enclosing an ovate, vibratile, flap-like membrane ; anal aperture 

 subterminal ; general surface of the body entirely and evenly ciliate ; no 

 larger adoral cilia ; cortical layer usually containing thickly set trichocysts ; 

 endoplast and contractile vesicle conspicuous. Inhabiting pond and bog 

 water. 



An additional and leading distinction of the genus Ophryoglena, as instituted by 

 Ehrenberg, is the presence, near the anterior extremity of the body, of a coloured 

 eye-like pigment-spot. More recent investigation has, however, shown that this 

 character is altogether subordinate, such a pigment-spot not being constant, either 

 with respect to its presence or location, even among zooids of the same species. 



Ophryoglena acuminata, Ehr. 



Body ovate, flattened, pointed and acuminate posteriorly, little over one 

 and a half times as long as broad ; colour brown ; oral fossa extending back- 

 wards to about the centre of the body ; a scarlet pigment-spot usually 

 present near the anterior extremity; contractile vesicle single, spherical, 

 situated in the median line towards the anterior extremity; endoplast 

 rounded, located a short distance behind the contractile vesicle. Length 

 1-180". HAB. Bog water. 



The habits of this animalcule are essentially phytophagous ; the diatom Navicula 

 gracilis, which, according to Ehrenberg, is an especially favourite food, being often 

 found in great numbers within the body-substance. 



Ophryoglena atra, Ehr. PL. XXVI. FIGS. 63 AND 64. 



Body ovoid, flattened, pointed posteriorly, nearly twice as long as 

 broad ; colour very dark and opaque, usually with a bluish pigment-spot 

 near the anterior extremity ; oral fossa broad and deep, extending back- 

 wards to nearly one-half of the length of the entire body, the membranous 

 flap occupying the posterior half of its cavity ; contractile vesicle single 



