566 DESCRIPTION OF {TolygastAca. 



ciliated in its anterior half ; cilia curved backwards. E-evolves on its 

 axis in progressing forwards. Length 1-1 000th. In sea water. 



AcoMiA (?) eostata. — Body ovoid-oblong, narrower in front ; appa- 

 rently inclosed by a thick membrane, or a more consistent layer, 

 nodular ; nodules often arranged in rows, as ribs. Division transverse. 

 Length 1 -650th to 1 -500th. In sea water, among Algae. 



A. varians. — Body oblong, cylindrical; truncated and angular in 

 front ; dilated and compressed, by turns, in different parts of its 

 length, and, consequently, alternately constricted behind, and termi- 

 nated by a pointed tail, or rounded. Revolves on its axis. Length 

 1-lOOOth to l-450th. 



Genus Gastroch^ta. — Body oval, convex on one side, and hollowed 

 by a longitudinal furrow on the other ; cilia seated in the furrow, 

 chiefly at the two ends. 



G. fissa. — Body semi-transparent, oval, truncate in front. Length 

 1 -408th. In the water of the Seine (P. 21, f. 18.) 



Genus Alysctjm. — Body ovoid-oblong, irregular, surrounded by 

 radiating cilia, and having, besides, a lateral bundle of long retractile 

 cilia, by means of which it leaps briskly from place to place. 



The single species resembles much Enchelijs nodulom {Pa/ramecium 

 milium, or Pantotrichum Enchelys, Ehr.) from which it is distinguished 

 by its retractile filaments. 



A. saltans. — Body colouiiess, oblong, rounded at the ends, rather 

 concave along the side, beaiing the retractile filaments, with some 

 almost invisible longitudinal furrows. Length l-1300th to l-1130th 

 In infusions and in the Seine (P. 21, f. 20.) 



Genus Ueonema. — Body long, narrower in front, rather cuiwed ; 

 surrounded by radiating ciHa, and bearing a long straight cilium 

 behind. 



U. marina. — Body colourless, semi-transparent, nodular, elongated ; 

 contracted in front ; slightly curved, with from four to five slightly 

 marked longitudinal striae. Length 1 -595th. In the Mediterranean. 

 (P. 21, f. 25.) 



