798 ORDER HYPOTRICHA. 



scattered ventral styles, and five anal styles ; four isolated and often 

 fimbriated caudal styles or setae developed along the posterior margin ; 

 endoplast linear, curved ; contractile vesicle single, spherical, situated imme- 

 diately beneath the origin of the right-hand anal styles. Inhabiting salt 

 and fresh water. Multiplying rapidly by transverse fission. 



Euplotes patella, Ehr. Pl. XLIV. Figs. 23-25. 



Carapace elliptical, anteriorly truncate, its upper lip or lamina triangular, 

 projecting above and considerably overlapping the anterior margin of the 

 peristome ; the inner and reflected border of the peristome represented by a ' 

 simple unciliated groove or channel; frontal styles six in number, three 

 scattered ventral styles, the two more posterior caudal styles branched or 

 fimbriated ; the dorsal, surface usually traversed by seven longitudinal 

 furrows ; endoplast band-like ; contractile vesicle single, situated near the 

 anal aperture. Length 1-196". Hab. — Salt and fresh water. 



This species, like many other Hypotricha, is subject to considerable local and 

 individual variation, chiefly evinced in this instance in the varying contour of the 

 carapace and in the character of its ornamentation. This carapace or cuirass, 

 while normally oval or elliptical, may be nearly circular or lozenge-shaped, broad 

 in the centre and much narrower at the antero-posterior extremities. The longi- 

 tudinal sulci again, which usually form a well-developed series extending from one 

 end to the other of the dorsal surface, are sometimes developed only in the posterior 

 region, or may be altogether absent. The number, character, and arrangement ot 

 the various stylate appendages appear always in this species to accord with that 

 normal formula given in the foregoing diagnosis. 



So long since as the year 1869* the author placed on record an observation con- 

 cerning an example of the species that up to within a recent date he has been 

 entirely unable to reconcile with the characteristic structure of either this special type 

 or any representative of the present order. In this instance long flagella-like cilia 

 were. reported as projecting from the anterior extremity, of a length and character 

 altogether distinct from those usually entering into the composition of the 

 peristomal fringe of either Euplotes or its nearest allied generic types. Assisted, 

 however, by the light contributed by the developmental phenomena of Aspidisca 

 costata, recorded in a previous page, and in which it has been shown that the peri- 

 stomal fringe of cilia commences its existence as a simple vibratile membrane, the 

 phenomenon now referred to becomes more intelligible. In numerous instances the 

 permanent vibratile membranes of various Infusoria, such as obtain in the genera 

 Condylostonia, Bkpharisvm, Pleuroiiema, and others, have been first interpreted and 

 figured as flagella, their true significance being demonstrated only through more 

 recent and carefully conducted investigation ; and in like manner it may be con- 

 sistently predicated that the supposed flagella observed on the occasion quoted 

 represented the undulating outline of the primary vibratile membrane of the type in 

 question previous to its splitting up into the ciliary adoral wreath that characterizes 

 the adult form. Inferring at the time that this animalcule represented a fully 

 developed adult individual, we proposed to distinguish it by the title of Euplotes 

 paradoxa in reference to the apparent abnormal presence of long flagella. The 

 author is now satisfied, however, that the form represented an example of Euplotes 

 patella, previous to the complete perfect development of its adoral ciliary wreath. 



A variety of Euplotes patella having evenly parallel sides and a more elongate 

 elliptical contour, has recently received from Wrzesniowski the subspecific title 

 E. patella van eurystomus. 



* 'Monthly Microscopical Journal,' vol. i. pl. xii. fig. 5, p. 291. 



