PROTOZOA : INFUSORIA. 73 



the bell or calyx is surrounded by a projecting rim or border, 

 called the " peristome," within which is a circular surface, the 

 "disc," forming the upper extremity of the so-called "rotatory 

 organ." The disc is surrounded by a fringe of vibratile cilia, 

 forming a spiral line which is prolonged into the commence- 

 ment of the digestive canal. Near the edge of the disc is 

 situated the mouth, which conducts by its entrance or "vesti- 

 bulum " into a fusiform canal or " pharynx," which terminates 

 abruptly in the abdominal cavity. The particles of food are 

 taken in at the mouth, descend through the short alimentary 

 canal, and enter the abdominal cavity, where they are subjected 

 to the general rotation of the "chyme-mass," being finally 

 excreted by an anal aperture which is situated near the mouth. 

 As in Paramecium, the body in Vorticella is composed of an 

 outer " cuticle," a central " chyme-mass," and an intermediate 

 " cortical layer," which contains a contractile vesicle and a 

 band-like nucleus. 



Reproduction in Vorticella may take place by fission, or by 

 .gemmation, or by a process of encystation and endogenous 

 division. In the first of these modes the calyx becomes in- 

 dented in a longitudinal direction — viz., from the pedicle to 

 the disc; and the groove thus formed becomes gradually deeper 

 until the calyx is finally divided into two halves supported 

 upon the same pedicle. On one of these cups a "pos- 

 terior'' circlet of cilia is then formed in addition to the 

 "anterior" circlet already existing {i.e., a fringe of ciha is 

 developed round that end of the calyx which is nearest the 

 attachment of the pedicle and furthest from the disc). The 

 cup (fig. 11, d), thus furnished with a circlet of cilia at both 

 extremities, is then detached, and swims about freely. Finally, 

 the anterior circlet of cilia disappears, and this end of the 

 calyx puts forth a pedicle and becomes attached to some 

 foreign object. A new mouth is now formed within what 

 was before the posterior circlet of cilia ; so that the position 

 and function of the two extremities of the calyx are thus 

 reversed. 



In the second mode of reproduction — namely, that by gein- 

 mation — exactly the same phenomena take place, with this 

 single difference, that in this case the new. individual is not 

 produced by a splitting into two of the adult calyx, but by 

 means of a bud thrown out from near its proximal extremity. 

 This bud is composed of a prolongation of the cuticular and 

 cortical layers of the adult with a cascal diverticulum of the 

 abdominal cavity or chyme-mass. It soon develops a posterior 

 circlet of cilia, the connection with the parent is rapidly con- 



