438 ORDER FLAGELLATA-EUSTOMATA. 



being the possession of a separately protrusible pharyngeal tube, apparently of a 

 corneous nature, and comparable to that met with in Frorodon, ^Nassiila, Chilodon, 

 and many other Ciliata. 



Entosiphon sulcatus, Duj. sp. Pl. XXIV, Figs. 31-34. 



Body oval, depressed, slightly narrower anteriorly, the frontal border 

 obliquely notched on the left-hand side ; the dorsal and ventral surfaces 

 usually traversed by four or five longitudinal furrows ; flagella equally 

 slender, inserted at a little distance from each other, slightly to the left and 

 close to the anterior notch, the posterior appendage or gubernaculum two 

 or three times the length of the body, the anterior vibratile one usually 

 shorter ; pharynx tubular, extending in a median line from the oral aperture 

 at the anterior extremity through nearly three-quarters of the entire length 

 of the body, independently exsertile ; contractile vesicle single, situated a 

 little behind the insertion of the flagella and to the left of the pharyngeal 

 tube ; endoplast spherical, located posteriorly towards the centre of the 

 left-hand border. Length of body i-i 2 50". Hab. — Pond water. 



The cuticular sulci, obliquely notched contour of the anterior border, and 

 enormous development of the pharyngeal tube, together with its protrusible properties, 

 serve to distinguish this type from the various species of Anisoiiema with which it 

 was originally included by Dujardin. Longitudinal fission, commencing at the 

 anterior extremity and separating the body into two equal moieties, has been observed 

 in this species by both Stein and Biitschli, the animalcule, preparatory to such 

 process, developing two additional flagella. The young zooids, according to Stein, 

 are perfectly smooth and pointed at each extremity. The contractile vesicle is 

 represented by this last authority as often exhibiting a rosette shape similar to 

 that of Anisonema gmndis, while a large ovate germ-mass may in like manner be 

 developed from the pre-existing simple spheroidal endoplast. After the death of 

 the animalcule the indurated cuticle, with the enclosed horny pharyngeal tube, 

 resists decay for a considerable interval, presenting under such conditions the aspect 

 delineated at PI. XXIV. Fig. 34. 



Fam. IX. SPHENOMONADIDiE, S. K. 



Animalcules free-swimming, persistent in shape, cuticular surface 

 indurated ; flagella two in number, one long and one short, both vibratile 

 and extended anteriorly ; oral aperture succeeded by a distinct tubular 

 pharynx ; endoplasm colourless, granular ; endoplast and contractile vesicle 

 conspicuous. 



Genus I. SPHENOMONAS, Stein. 



Animalcules free-swimming, persistent in shape, subfusiform, angular 

 or facetted ; flagella terminal, two in number, one long and the other short, 

 both extended and vibratile ; oral aperture situated at the base of the 

 flagella, followed by a distinct tubular pharynx, the distal end of which 

 usually communicates with the contractile vesicle ; endoplasm transparent, 

 granular. 



This generic group, as here defined, is made to include the genus Tropidocyphiis 

 of Stein, in addition to that of Sphcnomoiias as constituted by that authority ; the 



