GENUS TILLINA. 513 



spherical, subcentral; contractile vesicle spheroidal, of large size, posteriorly 

 located. Length of body I -280". 

 Hab. — Fresh water and infusions. 



The distinction between this form and the Colpoda cucttlltis of Dujardin, or 

 Colpidium ciiculliis cf Stein, is explained in the descripu-on given of the last-named 

 species. Although appearing under ordinary magnification, and formerly pronounced 

 to be ciHated only at the anterior extremit)', there is no longer room for doubt that the 

 entire surface of the body of this animalcule is also finely ciliate. The multiplica- 

 tion by fission of this species has been described at length by the last-named author, 

 this process in all instances, according to Stein's observations, being preceded by 

 encystment. Within its cyst the animalcule divides variably into either two, four, 

 eight, or as many as sixteen, spore-like bodies, which ultimately escape through the 

 rupture of the wall of their prison-house in a form which, while smaller, is in all 

 respects identical with that of the parent animalcule. Similar remoductive pheno- 

 mena have been recorded in connection with the genus Otostoma, but are at the 

 same time rare among the Ciliata, though of almost universal occurrence among 

 the more simple Flagellata. No act of conjugation or fusion of two animalcules is 

 mentioned by Stein as necessarily preceding the process of encystment and sporular 

 form of multiplication as above described. 



Colpoda parvifrons, C. & L. 



Body ovate, nearly twice as long as broad, rounded at both extremities 

 but widest posteriorly, the anterior end not recurved ventrally ; the outer 

 surface of the body distinctly though finely ciliate; contractile vesicle 

 posteriorly situated but not precisely terminal as in C. cucullus. Length of 

 body 1-600". Hab. — River water : Spree, near Berlin (C. & L.). 



Colpoda pigerrima, Cohn. Pl. XXVII. Fig. 24. 



Body elliptical, pointed at each extremity, about three times as long as 

 broad, the anterior end most attenuate and curved towards the ventral 

 aspect ; oral cleft at a distance of about one-third of the entire length of 

 the body from the anterior extremity; cuticular surface subdivided by 

 longitudinal and transverse striations into minute quadrate areas ; cuticular 

 cilia very short and fine, of equal size throughout, oral cilia forming a 

 projecting recurved tuft ; contractile vesicle situated close to the base of 

 the oral cleft. Length 1-780". 



Hab. — Sea water with decaying animal matter. 



The greater proportional length, surface ornamentation, and position of the 

 contractile vesicle readily distinguish this type from the two preceding species. 



Genus VI. TILLINA, Gruber. 



Animalcules free-swimming, persistent in shape, subreniform ; oral 

 aperture ventral, followed by a long, curved pharynx ; cuticular surface 

 entirely clothed with very fine vibratile cilia, a circle of longer cilia developed 

 round the oral aperture and continued down the pharyngeal passage ; 

 endoplast and contractile vesicle conspicuous. 



