62 MA NTT AT, OF ZOOLOGY. 



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 (i.e. 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, 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 csecal diverticulum of the 

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

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

 stricted until complete separation is effected, and then the 

 process differs in no respect from that described as occurring 

 in the fissiparous method of reproduction. 



In the third mode of reproduction the Vorticella encysts 

 itself in a capsule, the cilia and pedicle disappear, and the 

 nucleus breaks up into a number of rounded germs which are 

 ultimately liberated by the rupture of the cyst, and, after a 

 short locomotive stage, develop themselves into fresh Vorticellce. 

 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. 



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, 



