GENUS UROSTYLA. 765 



ciliate, nearly straight; from three to five anteriorly developed ventral 

 styles, which are supplemented by five even median rows of short ventral 

 setae ; the marginal setae forming a continuous projecting row ; anal styles 

 from seven to eight in number ; endoplast ovate, double. Length 1-84". 

 HAD. Fresh water. 



The Oxytricha urostyla of Claparede and Lachmann is identified by Stein with 

 this type, from which furthermore it does not seem possible to distinguish the 

 Oxytricha multipes of the same writers. A variety of this species is reported by 

 Mereschkowsky from Lake Onega, that is distinguished by the possession of six 

 instead of five rows of ventral setae. 



Urostyla grandis, Ehr. PL. XLIII. FIGS. 6-8. 



Body oblong or ovate, very variable in form, when extended about four 

 times as long as broad, usually widest posteriorly, the anterior extremity 

 tapering and obtusely pointed ; peristome-field triangular, its reflected 

 border ciliate, curved inwards at the apical extremity, the intervening 

 space between the inner and outer borders, and more especially towards the 

 right, thickly clad with fine vibratile cilia ; the entire angle to the right of the 

 reflected inner border, or that corresponding with that of the peristome-field 

 on the left side of this line, beset with the numerous claw-shaped frontal 

 styles, those nearest the anterior margin being the largest ; median ventral 

 setae usually developed in even longitudinal rows in such luxuriance as to 

 completely cover the remaining ventral surface, but occasionally a few only 

 of these rows represented ; marginal setae rather longer than the ventral 

 ones, forming an uninterrupted projecting fringe ; from ten to twelve short 

 anal styles ; endoplast cord-like, breaking up into numerous separate ovate 

 nodules ; contractile vesicle situated on the left side, near the posterior 

 angle of the peristome. Length 1-60". 



HAB. Pond water, among Conferva, &c. 



Stein attests to having carefully examined innumerable examples of this species 

 without finding, except in a few isolated instances, any trace of a nucleus or endoplast, 

 a circumstance which would seem to supply important evidence with respect to the 

 unessential character of this structure and to its nonconformity with the nucleus of 

 an ordinary histologic cell. The voracity of this large animalcule is remarkable, 

 several rotifers, a Coleps, and numerous diatoms and monads representing, as drawn 

 by Stein, the contents of a single individual's internal parenchyma. Although the 

 number of rows of the median ventral setae vary considerably in this form, the 

 location and arrangement of the anterior styles are constant and afford a safe guide 

 to the recognition of the species, which is moreover the largest known representative 

 of the Hypotrichous order. 



The Oxytricha fusca of both Perty and Claparede and Lachmann is regarded 

 by Stein as identical with this type. 



Urostyla viridis, Stein. 



Body lanceolate, three and a half times as long as broad, the two 

 extremities pointed, the anterior one curved slightly towards the left ; 

 peristome-field narrow, extending obliquely backwards to about one-third 

 of the length of the entire body, exhibiting no reflected inner border ; frontal 



