PROTOZOA;: INFUSORIA. 99 



as occurring in the fissiparous method of reproduction. According to 

 Stein and Greeff, however, these so-called "buds" are really small calyces, 

 produced by fission of one Vorticella and then attaching themselves to the 

 outside of the calyx of an6ther individual. 



In the third mode of reproduction the Vorticella encysts itself in a cap- 

 sule, 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 Vorticella, 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 rigid and not contractile. It 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 sarcode-body enclosed within the cortical layer 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. 



Carchesium is another form which is like Epistylis in consisting of a 

 number of calyces supported upon a branched pedicle, but differs from Epi- 

 stylis and agrees with Vorticella in the fact that the pedicle is contractile. 



Stentor, or the trumpet-animalcule (fig. 33, A), is another common In- 

 fusorian which is closely related to Vorticella. It consists of a trumpet- 

 shaped calyx, devoid of a pedicle, but possessing the power of attaching 

 and detaching itself at will. When detached it swims by means of the 

 anterior circlet of cilia, just as the calyx of Vorticella will if broken from 

 its stalk. In Vaginicola (fig. 33, B) the essential structure is much the 

 same as in Vorticella, but the body is protected by a membranous or horny 

 case ("carapace" or "lorica"), which is formed by a hardening of the 

 cuticle, and within which the animal can retire. 



II. ORDER SUCTORIA. This order includes a series of In- 

 fusoria of a very anomalous nature. In Acineta or in Podo- 

 phrya (fig. 34, A), which may be taken as types, the body is 

 provided with a number of radiating filamentous tubes, which 

 are furnished at their extremities with suctorial discs, and are 

 capable both of exsertion and retraction. These retractile 

 tubes both seize the prey and serve as vehicles for the ingestion 

 of food : hence the term " polystome," or many-mouthed, has 

 been proposed for the order by Professor Greene. A nucleus 

 and one or more contractile processes are present, but they 

 possess no cilia in their adult condition, and the body is fixed 

 to some foreign object by a stalk-like extension of the cortical 

 layer. 



III. ORDER FLAGELLATA. This order comprises those In- 



