8o MANUAL OF ZOOLOGY. 



the mouth, which conducts by its entrance or " vestibulum " 

 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 and within 

 the vestibule. As in Param&cium, 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. The cortical layer appears 

 to be furnished with muscular fibres, and the contractile stem- 

 fibre is almost certainly a muscle. 



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 " posterior " 

 circlet of cilia is then formed in addition to the " anterior " 

 circlet already existing (/>., a fringe of cilia is developed round 

 that end of the calyx which is nearest the attachment of the 

 pedicle and furthest from the disc). The cup (fig 16, 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 gem- 

 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 caecal diverticulum of the 

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

 circlet of cilia, the connection with the parent is rapidly 

 constricted until complete separation is effected, and then the 

 process differs in no respect from that described as occur- 

 ring in the fissiparous method of reproduction. According to 

 Stein and Greif, however, these so-called "buds" are really 

 small calyces, produced by fission of one Vorticella and then 



