GENUS TRICHONEMA—MITOPHORA. 469 



The members of this group, as typified by the genus Trichonema of De 

 Fromentel * may be said to bridge over the gap between the ordinary Flagellata 

 and Holotriclious Cihata, in the same manner as the Stephanomonadidcz connect 

 them with the Peritricha. In the absence of the flagellum the animalcule in 

 question would scarcely be distinguished from a minute Trachelophyllum or other 

 representative of the Holotrichous order. 



Genus I. TRICHONEMA, De Fromentel. 



Animalcules free-swimming, more or less ovate, elastic and changeable 

 in form, bearing a single flagellum at the anterior extremity ; the entire 

 cuticular surface clothed with short cilia ; oral aperture distinct, situated at 

 the base of the flagellum. 



Trichonema hirsuta, From. Pl. XXIV, Figs. 65 and 66. 



Body when extended subpyriform or ovate, most usually rounded and 

 inflated posteriorly, narrower and attenuate anteriorly, contracting to an 

 almost globular form; endoplasm hyaline, granular; flagellum long and 

 slender, about twice the length of the body, rigid at its base, very flexible 

 and undulating at its distal extremity; cuticular cilia short and apparently 

 non-vibratile ; oral orifice represented by an obliquely oval excavation, 

 situated at the base of the flagellum ; contractile vesicle posteriorly located. 



Length 1-800". Hab. — Fresh water. 



Genus II. MITOPHORA, Perty. 



Animalcules free-swimming, persistent in shape, elongate-ovate or 

 pyriform, bearing a single terminal flagellum which is supplemented by a 

 lateral or more or less complete peripheral fringe of vibratile cilia. 



In the single type referred to this genus by Perty, a considerable range of varia- 

 tion is, in accordance with his accompanying figures, exhibited in the development of 

 the accessory cilia. In some instances these appendages are represented as formino- 

 a short lateral fringe only, while in others they constitute an almost complete 

 peripheral series. It would seem, indeed, not altogether improbable that these cilia 

 entirely clothe the cuticular surface as in Trichonema, from which generic type it 

 would then be distinguished only by its persistent shape. 



Mitophora dubia, Perty. Pl. XXIV. Figs. 67 and 68. 



Body clavate or pyriform, sometimes curved, from two to three times 

 as long as broad ; flagellum produced from the thicker of the two 

 extremities, sometimes with a knob-like distal termination ; lateral ciliary 

 fringe conspicuous, variably developed; endoplasm enclosing green granules. 

 Length 1-450". Hab. — Fresh water ; movements slow and rotatory. 



Some uncertainty is attached to the identification of the anterior and posterior 

 regions of this animalcule, Perty correlating with the latter the extremity bearing 

 the flagelliform appendage. In one of his figures, however, a notch-hke excavation 

 is indicated close to this organ, and this not improbably -represents an imperfectly 

 observed oral aperture. 



* ' Etudes surles Microzoaires, ' Paris, 1876. 



