746 ORDER HYPOTRICHA. 



widest anteriorly, and bent upwards towards the dorsal aspect, entirely 

 ciliate ; the oral aperture anteriorly situated, pharynx enclosing a cylindrical 

 rod-fascicle. HAB. Fresh water. 



Phascolodon vorticella, Stein. PL. XLII. FIGS. 14 AND 15. 



Width of the truncate anterior margin equal to or exceeding half the 

 length of the body, sharply pointed posteriorly ; the dorsal surface much 

 elevated and inflated ; cilia most conspicuously developed round the anterior 

 margin and the posterior half of the ventral surface ; endoplast central, oval, 

 containing a minute spheroidal endoplastule ; contractile vesicles two in 

 number, one stationed in front of and the other behind the endoplast. 

 Length of body 1-288". HAB. Fresh water. 



Viewed from the dorsal surface, this animalcule, with its convex back and 

 ciliated anterior margin towards the observer, presents the aspect of a free Vorticella, 

 and it is only when turning over and thus exhibiting its flat ventral surface and cha- 

 racteristic pharyngeal rod-fascicle, that its true nature becomes apparent. Stein 

 never observed this species creep over aquatic substances after the manner of 

 Chilodon and its other nearest allies, its habitual motion being that of uninterrupted 

 rotation through the water. This peculiarity, together with its characteristic form, 

 distinguishes this type essentially from the ordinary Hypotricha, and would seem, as 

 intimated by Stein, to indicate its true position as transitional between the last- 

 named order and that of the Peritricha. The younger forms of Phascolodon, with 

 the exception of being somewhat more attenuate, differ but little from the adults, 

 and are referred to by Stein as presenting some superficial resemblance to Ehren- 

 berg's Trichodina vorax* 



GENUS II. CHILODON, Ehrenberg. 



Animalcules persistent in shape, but more or less flexible, subovate, 

 produced anteriorly into a lamellar, lip-like prominence ; the dorsal region 

 convex, the ventral surface perfectly flat, entirely ciliate ; oral aperture 

 debouching upon the centre of the anterior body-half, succeeded by a tubular 

 pharynx, associated with a cylindrical rod-fascicle, the anterior or distal 

 edges of which are protrusible beyond the cuticular surface ; anal aperture 

 postero-terminal ; dividing by both transverse and longitudinal fission. 

 Inhabiting salt and fresh water. 



Chilodon cucullulus, Mull. sp. PL. XLII. FIGS. 16-22. 



Body very flexible, subovate, twice as long as broad, rounded poste- 

 riorly, the lip-like projection of the anterior extremity sharply pointed, 

 curved towards the left ; the ventral surface ciliate throughout, but the 

 cilia larger and more conspicuous on the front margin and left side of the 

 anterior extremity ; an undulating line or groove leading diagonally from 

 the apex of the lip-like prominence to the oral aperture ; endoplast ovate or 



* A reference to this very doubtful species was inadvertently omitted in the account already 

 given of the genus Trichodina (pp. 645 to 649). So far as it is possible to judge from Ehrenberg's 

 figures and brief description the type would appear to represent either an elongate species of Strom- 

 bidium or the detached zooid of some attenuate sedentary Vorticellidan, such as EpittyUt digitalis 

 or E. anastatica. 



