T. W. Engelmann on the Infusoria. 259 



DllEPANOSTOMA. 



Figure of body constant, but flexible, elongated, tapering 

 gently in front and behind; ventral aspect flat, dorsal convex; 

 the whole undersurface traversed by longitudinal strise, with 

 cilia of uniform length. The dorsum is smooth, but bears along 

 each margin a row of bristly cilia. Mouth placed beneath a 

 crescentic horny band not far from the anterior extremity, and 

 close to the left margin of the body. Nuclei two, each with a 

 nucleolus ; no sharply circumscribed contractile space. 



D. striatum, 



the only species yet determined, is allied on the one side with 

 hypotrichous Ciliata, such as Ckilodon, and, on the other, with 

 holotrichous Amphilepti. On account of the cilia being limited 

 to the ventral surface, it must be placed among the hypotrichous 

 Infusoria. The anal outlet is on the dorsal surface, not far from 

 the posterior extremity. The body is from 4 to 5 times as long 

 as broad, and somewhat pointed at its two ends. Fission not 

 observed. Size from 0'185 to 0*25 mill. 



Gastrostyla. 



Figure constant ; body loricated, elliptic, contracted anteriorly, 

 and more or less obtusely rounded posteriorly. Five or six 

 strong unciform setae are situated on the anterior extremity, and 

 a row of bristly cilia stretches obliquely across the ventral sur- 

 face as far as the four or five strong cilia about the anal orifice, 

 beyond which only a few extend to the posterior border. The 

 two rows of marginal cilia increase in dimensions posteriorly, 

 and overlap no seta? at the posterior extremity. Nuclei four. 



G. Steinii 



was noticed in January 1860, and belongs to the larger forms 

 of Oxytrichina. It is two and a half times as long as broad. 

 The frontal region is surmounted by a semilunar labium. The 

 peristome is small in diameter; on its inner margin a strong 

 undulating membrane is attached. The oblique row of setae, 

 stretching from the first adoral cilia in a gently curved line to 

 the five or six strong cilia about the anal outlet, is a charac- 

 teristic feature of the genus. Three stout uncinate setse are 

 inserted on the frontal region, and anteriorly to the oblique row 

 of cilia are two other such setse, and behind the angle of the 

 mouth from one to three powerful cilia. A remarkable feature 

 in this species, as in Onychodromus, is the existence of four 

 nuclei, each with its nucleolus, situated in a line one behind the 

 other. Movements rapid, not long in one direction. Fission 

 proceeds as in Stylonychia Mytilus. The four nuclei coalesce 



18* 



