70 MANUAL OF ZOOLOGY. 



short locomotive stage, develop themselves into fresh Vorticellcz. 

 How far this process may be truly sexual is not known, and 

 no form of unequivocal sexual reproduction has hitherto been 

 shown to occur in the case of Vorticella. 



Fig. ii. a Vaginicola crystallina ; b Stentor Mnllert ', c Group of Vorticelloe .* 

 d Detached bud of Vorticella, showing the posterior circlet of cilia. 



Epistylis is a not uncommon form of fixed Infusorian which 

 is nearly allied to Vorticella, and differs chiefly in the fact that 

 the pedicle is much branched, and is rigid and not contractile. 

 Epistylis (fig. 10, a) usually occurs in the form of a greyish- 

 white nap on the stems of water-plants, or on the head of 

 the common water-beetle, the Dytiscus marginalis. It consists 

 of a plant-like branching and re-branching frond, the stems of 

 which are quite transparent and faintly striated, but are not 

 contractile, though capable of movement from side to side. 

 Each branch of the entire colony terminates in an oval calyx, 

 articulated to the stem by a distinct joint, upon which it can 

 move from side to side. The calyces are oval or somewhat 

 campanulate, but have the power of altering their dimensions, 

 and especially of contracting so as to shorten their antero- 

 posterior diameter. Each calyx terminates distally in a 

 slightly elevated annular aperture, the margins of which are 

 regularly toothed. The calyx appears to be formed by a 

 hardening of the cuticle, and to form a distinct case, with a 

 double margin, enclosing the animal. The sarcode body en- 

 closed within this outer envelope is of a light brown colour 

 and full of minute granules, with larger food-vacuoles and a 

 well-marked contractile vesicle, which contracts and dilates 

 two or three times a minute. The animal can retract itself 

 entirely within its cup, and can at will exsert a ciliated disc. 

 This disc (fig. 10, b) is inversely conical, and acts as a kind of 



