525 DESCEIPTION OF [Tolygastrica. 



Gt nus VoRTicELLA. — The hell -shaped Animalcides are cro\rrccl with 

 cilia anteriorly, and have a pedicle or stalk, when yonng, but which, 

 at a later period, and also after the first self- division, is wanting. 

 Their shape, when pedicnlated, is similar ; the pedicle can be sud- 

 denly deflected, spirally, by means of the long muscle within it, but 

 it is never branched. The wreath of cilia and the long muscle, with the 

 hollow pedicle, are the organs of locomotion. At certain periods a second 

 wreath of cilia is 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. 

 But in the genera Epistylis and Opercularia, whose pedicles are com- 

 paratively motionless, the nutritive apparatus maybe much more 

 accuratelj^ investigated. The mouth and discharging orifice are 

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

 propagative structures are variously coloui'ed ; clusters of ova, an 

 elongated gland, and a round contractile bladder, exist ; in fine, the 

 animalcules are androgjTious. 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 animal- 

 cule loosens itself from its pedicle or stalk, a cii'cumstance, which 

 (says Ehrenberg) " takes place at certain periods, the stalks die, or 

 disappear, just like the sheUs of crabs, or as the nails and haii-." 

 The muscular fibre within the stem, requires stops, or an achromatic 

 condenser, under the stage, to render it distinct. 



The Vorticellae being of so considerable size, and easily pro- 

 curable, have formed the subject of numerous iuvestigations into theii' 

 organism; but yet no observers have been able to coincide entu'ely with 

 the views of Elirenberg. Among the most recent researches are 

 those of Dr. Stein, of Berlin, which are devoted chiefly to the eluci- 

 dation of the phases of development of Yorticellina ; but which 

 refer also to their general organization. Stein describes a canal, 

 extending from the mouth into the inteiior of the body, and lined 

 with cUia ; this tube, however, does not ciu-ve on itself, so as to 

 ajiproximate its two extremities, but ha\ iug advanced to about the 

 ccatic of the body, ends abrupt!} b}- an open extremity, (P. 22, f. 1.) 



