80 PROFESSOR O. BiJTSCHLI. 



author believes that these cysts bear some relation to Dino- 

 hryon sertularia. The formation of the two sheaths calls to 

 mind the condition in Nuclearia simplex, which was first 

 observed by Cienkowski. 



Trepomonas, Dujardin {' Histoire nat. des Infusoires/ 

 Paris, 1841, p. 294). \ , 



Trepomonas agilis, Dujardin (op. cit., p. 294, pi. iii, 



Trepomonas agilis^ Perty (' Zur kenntniss kleinster Lebens- 

 formen nach Bau, Function, Systematik,^ &c., p. 171, pi. xiv, 

 fig. 15). 



Trepomonas agilis, Fromentel ('Etudes sur les Micro- 

 zoaires,' Paris, p. 334, pi. xxvii, fig. 16). 



Gri/mcea vaccillans, Fresenius (" Beitrage sur Kenntniss 

 kleinster organismen," * Abhl. der Senkenberg. Geschellsch. 

 zu Frankfurt-a M.,' Bd. ii, pi. x, figs. 48, 49). 



This is one of the most interesting of the Flagellate forms ; 

 it is tolerably common in rather dirty water, and is some- 

 times found in immense numbers in infusions. The organ- 

 isms are difficult to observe properly, on account of their 

 almost constant and peculiar screw-like movement. The or- 

 ganism is oval and somewhat flattened (PI. VI, fig. 14, a, b, c), 

 the hinder end is generally broader in a noticeable degree than 

 the anterior. The long sides are drawn out and broadened 

 into delicate wings, which are bent outwards laterally, in 

 contrary directions, towards the broad sides, in such a way 

 that the transverse section of the body presents the form of 

 an S. These reflexed expansions are small and feeble at 

 the anterior end of the body, increasing gradually as they 

 pass backwards, till they present a considerable surface. The 

 flagella are always, when the organism is observed laterally, 

 directed obliquely away from the body (fig. 14, b). In a 

 surface view from above (fig. 14, a) they are seen to be bent 

 in such a way as to correspond with the screw-like expan- 

 sions, and are uniformly thick filaments. As a result of this 

 arrangement of the flagella the little organisms move through 

 the water with rapid undulations, the screw-like end back- 

 w^ards, and the flagella in front. The internal arrangement 

 of these little living screws is just as interesting as the 

 external formation. Trepomonas is undoubtedly an animal 

 Flagellate, which ingests solid nutriments, although the 

 precise spot at which it is taken in has not been observed = 

 The numerous food particles, such as Bacteria, enclosed in 

 the very clear and transparent protoplasm, leaves no doubt 

 as to its mode of nutrition. The author has been unable to 



