640 ORDER PERITRICHA. 



Fam. V. GYROCORID^, Stein. 



Animalcules free-swimming, persistent in shape, but not encuirassed, 

 ovate or pyriform, provided with one or more spiral or circular wreaths 

 of cirrose cilia ; oral aperture lateral or ventral ; anal aperture postero- 

 terminal ; the posterior extremity frequently bearing a conspicuous stylate 

 or more or less flexuose caudal appendage. 



The three genera included in this family group differ from all remaining 

 representatives of the Peritricha in the lateral location of the oral aperture. 

 Through Urocentrum a close relationship with the Heterotrichous genus Calcedus is 

 evidently established. 



Genus I. GYROCORIS, Stein. 



Animalcules free-swimming, persistent in shape, separated into two 

 conspicuously distinct regions, the anterior one helmet-shaped or cam- 

 panulate, more or less rounded anteriorly, with a free mantle-like 

 posterior border, the hinder portion produced from the centre of this 

 border as a long claw-like style or tail ; a ciliated groove extending back- 

 wards from the anterior extremity along the ventral surface, then ascend- 

 ing obliquely and continued as a right-winding spire of long, powerful 

 locomotive cilia, which form a fringe round the free truncate margin of the 

 anterior or body portion ; oral aperture situated apparently near the centre 

 of the ventral ciliated groove; anal aperture posteriorly located; contractile 

 vesicle and endoplast conspicuous. 



Gyrocoris oxyura, Stein. Pl. XXXIII. Figs. 1-6. 



Body bell- or helmet-shaped, subpyriform ; claw-like tail or style 

 produced from the hinder margin, equalling the body in length ; cilia 

 forming the posterior marginal fringe very long and fine ; contractile 

 vesicle large, spherical, situated close to the base of the tail-like portion ; 

 endoplast represented by three or four, more rarely two, transversely 

 disposed ovate corpuscles ; a bluish, granular, crescent-shaped spot, corre- 

 sponding probably with the so-called eye-speck of other infusorial forms, 

 often present at the anterior extremity. Length, including tail, 1-200". 



Hab. — Stagnant water. 



This form was first obtained by Stein in great profusion in stagnant water near 

 Prague, and is described by him * as exhibiting such rapidity of motion, through 

 revolution on its axis in a screw-like manner, that the greatest difficult)' attends the 

 interpretation of its true form and character ; the oral aperture under these con- 

 ditions, while suspected to be situated in the ciliated ventral groove, was not 

 absolutely observed. The possible affinity of this form with the imperfectly described 

 Ccenomorpha medusula of Perty and the Trichodina Unfaculata of Ehrenberg has been 

 recognized by Stein ; in both of these, however, the body portion appears to be more 

 nearly hemispherical or discoidal ; there is, again, no indication of a ventral ciliated 

 groove, and such cilia as are represented, though possibly erroneously, form a fringe 

 round the anterior border. An animalcule figured by Mr. Tatem in the ' Quarterly 



• ' Sitrungsbericht der K. Bohmischen Ges. d. Wiss.,' S. 48, 1S60. 



