GENUS ANOPLOPHRYA. 563 



title of 'Animalcula in stercore Ranarum.' By Stein it has been more recently 

 referred to the next genus, Anoplophrya, but in the absence of all trace of 

 the contractile vesicle, which forms so distinctive a feature of the members of that 

 generic group, it appears desirable to retain it among the ordinary Opalina. Sub- 

 division by longitudinal and transverse fission, and the production through this 

 process of reproductive cysts, as in the previously described species, has been 

 observed by Zeller, who has, however, without sufficient apparent cause, proposed 

 to substitute for this form the title of Opalina similis. 



Opalina caudata, Zeller. PL. XXVI. FIGS. 23 AND 24. 



Body irregularly ovate, about twice as long as broad ; the dorsal surface 

 convex and inflated, the ventral one flattened ; the posterior extremity 

 produced as a short, conical, tail-like appendage ; cuticular striae obliquely 

 directed, widely separated in comparison with those of the preceding 

 species ; endoplasts two in number, subcentral, united to each other by a 

 sinuous thread-like commissure ; dividing by longitudinal and transverse 

 fission. Length 1-120". HAB. Intestine of Bombinator igneus. 



The multiplication of this species through the minute subdivision and cyst- 

 formation of the primary zooids, as in the four preceding types, was observed by 

 Zeller to take place during the months of April, May, and June. A distinctive 

 feature of this species, in addition to its characteristic contour, is afforded by the 

 wide separation of the cuticular striations, and by the apparent density of the clear 

 cuticular layer. In the possession of two connected endoplastic bodies this type 

 agrees with the form last described. At the time of segmentation these two 

 structures become isolated within the anteriorly and posteriorly separated moieties, 

 but quickly double themselves again by redivision. Not unfrequently, the sub- 

 division of the endoplasts precedes the segmentation of the animalcule's body, 

 which is therefore for a while provided with four endoplastic structures. 



GENUS II. ANOPLOPHRYA, Stein. 



Animalcules mouthless, free-swimming, ovate or elongate, entirely 

 ciliate ; endoplast conspicuous, mostly band-like, and axial ; contractile 

 vesicle or vesicles well developed ; possessing no supplementary organs 

 of prehension. Occurring as parasites within the intestinal viscera of 

 various Invertebrata. 



Anoplophrya naidos, Duj. sp. PL. XXVI. FIG. 12. 



Body variable in form, elongate-ovate or elliptical, considerably flat- 

 tened, bluntly rounded at each extremity, the anterior one sometimes 

 obliquely truncate, averaging from three, to four or five times as long as 

 broad ; cuticular surface longitudinally furrowed or striate, entirely ciliate ; 

 contractile vesicles numerous, usually disposed in a single line down one lateral 

 border, occasionally forming a second line on the opposite side ; endoplast 

 axial, thick and band-like, coarsely granular, extending nearly the whole 

 length of the body. Length 1-200". 



HAB. Intestine of Nats serpentina. 



The highly developed contractile vesicles of this species were not recognized by 

 Dujardin when he first described it under the name of Opalina naidos, but have 



