258 DESCRIPTION OF [Polygastrica. 



foot. Found amongst lemna and conferva. Figure 232 

 is a dorsal view, and 231 a side view. Size 1 -430th to 

 1 -280th. 



Genus XC. VORTICELLA. The bell-shaped Animalcules 

 are crowned with cilii anteriorly, and have a pedicle or 

 stalk, when young, but which, at a later period, and also 

 after the first self- division, is wanting. Their shape, when 

 pediculated, is similar 5 the pedicle can be suddenly de- 

 flected spirally by means of the long muscle within it, 

 but it is never branched. The wreath of cilii, and the 

 long muscle, with the hollow pedicle, are organs of loco- 

 motion. At certain periods a second wreath of cilii is 

 said to be produced at the posterior part of the body. Not 

 only can numerous stomach-cells be seen, but likewise, 

 according to Ehrenberg, the gradual passage of the food 

 onwards, in a twining sort of intestinal canal, though he 

 says the latter is not easily observed, on account of the 

 periodical deflection of the pedicle. On this account it is 

 more satisfactorily seen in the genera Epistylis and Oper- 

 cularia. The mouth and discharging orifice are separate, 

 but lie in the same hollow, at the anterior margin. The pro- 

 pagative structures are variously coloured; clusters of ova, 

 an elongated gland, and a round contractile bladder, exist ; 

 in fine, the animalcules are androgynous. The supposed 

 increase by the growth of young animalcules out of the 

 pedicle, like flowers on the stem of a plant, has arisen 

 from erroneous observation. When the animalcule loosens 

 itself from its pedicle or stalk, a circumstance which, says 

 Ehrenberg, ft takes place at certain periods, the stalks die, 

 or disappear ; just like the shells of crabs, or as nail and 

 hair. 5 ' The muscular fibre within the stem requires stops, 



