GENUS UROTRICHA. 505 



various minute entirely ciliate forms too indistinctly characterized for present 

 identification, and in none of which is mention made of the terminal springing- 

 hairs upon which the genus Urotricha is mainly founded. 



Urotricha farcta, C. & L. PL. XXVII. FIG. 2. 



Body ovate or ellipsoidal, surface of cuticle coarsely and obliquely 

 striate ; cilia short and evenly distributed, posterior springing - hair 

 obliquely directed when at rest, about equal to the body in length ; oral 

 aperture perforating a small circular prominence at the anterior extremity. 

 Contractile vesicle single, spherical, posteriorly situated ; endoplast ovate, 

 subcentral. Length 1-1250". HAB. Pond water and in infusions. 



The movements of this animalcule are of two kinds, and somewhat remarkable. 

 In its more ordinary mode of progression it swims slowly in a forward direction, 

 describing circles of a considerable diameter, the organs of propulsion on such 

 occasions being the irregularly vibrating cuticular cilia ; now and then, however, 

 this more even locomotion is interrupted by a spasmodic leap to one side or in some 

 other direction, the motion in this instance being accomplished by the posterior 

 seta or springing-hair. According to its discoverers, the oral aperture of this 

 species is capable of slight protrusion anteriorly in a lip-like manner, and in a way 

 apparently according with that characteristic of Trachelophyllum apiculatum and 

 Enchelyodon farctum ; its walls are at the same time highly elastic, and permit the 

 passage of food-masses almost equal in size to its own body. 



Urotricha lagenula, Ehr. sp. PL. XXVII. FIG. i. 



Body flask-shaped or pyriform, attenuate in front, rounded posteriorly, 

 from one and a half to twice as long as broad ; cuticular surface smooth ; 

 cilia longest in the anterior region, moving independently ; posterior spring- 

 ing-hair always directed backwards in a straight line, exceeding the body in 

 length ; contractile vesicle single, spherical, posteriorly located. Length 

 1-570". HAB. Pond and marsh water. 



This species, apparently identical with the Pantotrichum lagenula of Ehrenberg, 

 differs from the preceding type, not only in its larger size, but in its flask-shaped 

 contour, in the greater development of the cilia in the anterior region, and in 

 the uniformly straight direction of the posterior springing-hair, which has, moreover, 

 a greater proportional length. In common with Urotricha farda, its movements 

 through the water consist of slow rotation on its longitudinal axis in circles 

 and in a forward direction, varied by occasional leaps from side to side after the 

 manner of a Halteria or Uronema. In examples obtained from marsh water in the 

 neighbourhood of Le Marais, Jersey, in company with Paranuzcium bursaria, 

 numerous green chlorophyll-granules occupied almost the entire space of the internal 

 endoplasm; this colouring-matter was doubtless derived from the inception of 

 zoospores, Thecomonads, and other chlorophylloid organisms which abounded in 

 the same locality. The almost invariable occurrence of this form in company 

 with Hal'-ria grandinella, has afforded the author grounds for suspecting that 

 Urotricha lagenula may eventually prove to be a developmental phase only of the 

 last-named animalcule. 



Fam. IV. COLEPID-ffi, Ehrenberg. 



Animalcules free-swimming, symmetrically ovate, persistent in form, 

 ciliate throughout, oral cilia slightly larger than those of the general 

 cuticular surface. 



VOL. II. D 



