Infusoria from American Fresh Waters. 105 



nucleus moniliform, the nodules ovate, numerous ; trichocjsts 

 abundant, most conspicuously developed as a dense, radiating 

 series within the frontal border ; anal aperture at some dis- 

 tance from the posterior extremity ; endoplasm granular. 

 Length of the extended mature body -^^ to gV inch. 



Bah. Standing pond- water. 



The largest and mature zooids are visible to the naked eye 

 as fine white threads gliding through the water. 



Chihdon vorax, sp. nov. (PL III. fig. 2.) 



Body suboval, soft and flexible, twice and a half as long 

 as broad, widest anteriorly, and curved towards the left- 

 hand side, gradually tapering from the sinistral concavity to 

 the rounded posterior extremity, the left-hand border slightly 

 convex, the lip-like projection obtuse or rounded ; cuticular 

 surface longitudinally striate ; nucleus elongate-ovate or sub- 

 fusiform, located in the posterior body-half, usually near the 

 right-hand lateral border ; contractile vesicles multiple, small, 

 spherical, scattered ; an undulating line of cilia extending from 

 the lip, beyond which it frequently projects, to the oral aper- 

 ture; anal aperture dorsal, near the posterior extremity. 

 Length of body y^-g- inch. 



Hab. Fresh water, with Oscillaria and other algge in early 

 spring. 



The rod-fascicle lining the pharyngeal passage is not only 

 somewhat protrusible, as in the other members of the genus, 

 and expansile and contractile at the distal extremity, but it is 

 also freely movable within the body-sarcode around the 

 margin of oral attachment as a centre. The Infusorians under 

 observation fed voraciously on certain linear diatoms (pro- 

 bably a species o^ Nitzschia) with which the water teemed, the 

 frustules often being considerably longer than the body of the 

 animalcule in its normal condition, and, after being engulfed, 

 consequently extending through the entire length of the Infu- 

 sorian, and stretching the cuticular surface at both extremi- 

 ties until at these points the limiting membrane became the 

 merest film. Before the process of engulfing was actually 

 witnessed it was an interesting problem as to how the diatom 

 became freed from the posterior region of the pharyngeal 

 passage which extends almost to the centre of the body. The 

 first supposition was that the posterior extremity of the body 

 was sufficiently protruded under the pressure of the inflexible 

 diatom to allow the latter to pass from the pharynx and then 

 to glide forward, thus partially relieving the posterior pres- 

 sure. This supposition was not correct. During the passage 

 of the frustule, when the cuticular surface of the rear margin 



