90 PROFESSOR O. BUTSCHLI. 



forward movement is effected. The larger ilagellum rising 

 somewhat further behind is directed backwards by the move- 

 ment, and so it often simply trails till it attaches itself, and 

 then, by its rapid bending movements, it throws the body 

 backwards and forwards, but chiefly backwards, upon the 

 same spot. It is this flagellum to which Clark, in contrast 

 to the first one, has applied the term " gubernaculum." 



An integument is present, which has been investigated, 

 with a view to separating the three genera included here 

 under one name. Forms of unvarying shape, the surface 

 of which did not appear to be of a sticky nature, so 

 that foreign bodies adhered to it, were considered as being 

 provided with a firmly resisting integument, or a coat of 

 mail, and were placed in the genus Anisonema ; whilst on the 

 other hand the genus Heretomita was recognised by the 

 absence of such an integument. Mobile forms, such as 

 Euglena and Astasia, are distinguished by the possession of a 

 contractile integument, and this character serves also to dif- 

 ferentiate the genus Heteronema. 



As numerous Euglena-like organisms are known to possess 

 a very resisting and cuticle-like covering, so it is possible 

 that this character sharply differentiates in some degree the 

 genus Heretomita. On this account the author has had some 

 hesitation in associating Heteromita of Dujardin with the 

 organisms now described. 



Anisonema acinus, Dujardin ('Hist. Nat. des Infu- 

 soires,' Paris, 1841, p. 345, pi. iv, fig. 27). 



(?) Heretomita ovata, Dujardin (op. cit., p. 298). 



Anisonema cojicavum, Clark (' Ann. and Mag. Nat. Hist.,* 

 4th ser., vol. i, p. 254, pi. vii, figs. 65—69). 



Heteromita crassa, Fromentel ('Etudes sur les Micro- 

 zoaires,' Paris, p. 335, pi. xxiii, fig. 16). 



Diplomita insignis, Fromentel (op. cit., p. 335, pi. xxxiii, 

 fig. 37). 



This is a somewhat flattened organism ; the ventral 

 surface, upon which it generally advances, appears hollowed 

 so as to be slightly concave, whilst the dorsal surface is cor- 

 respondingly convex. The outline of the broad sides is 

 nearly oval, and usually the hinder part is somewhat broader 

 than the anterior, which is somewhat pointed, although — as 

 a comparison of fig. 19 a with 19 c will show — there is no rule 

 in regard to this. The small flagellum causing movement 

 arises from the most anterior point of the organism. The 

 concavity of the ventral surface is not quite in the centre ; 

 but extends somewhat lower on the right side by the 



