INFUSOKIA. 



41 



improbable that the contractile vesicles shcjvild be looked upon as 

 corresponding with the water-vessels of the lower groups of AVorms, 

 and as having the function of excretory, rather than of circulatory 

 organs. 



Reproduction in ParanKxcium may be effected simply by trans- 

 verse cleavage or fission of the body into two portions (fig. 19, B). 

 In other cases "conjugation" of two Paramixcia takes place. In 

 this process two individuals come together, and adhere closely to one 

 another by their ventral surfaces, in such a way that they present 

 the appearance of a single individual undergoing longitudinal fission 

 (fig. 19, C). Partial fusion of the conjugating individuals takes place, 

 and tlie nucleus and nucleolus pass through certain curious changes. 

 Ultimately, the conjugating individuals separate again, and each 

 probably then undergoes repeated fission, and thus gives rise to fresh 

 Paramixcia. 



As a common and beautiful example of the Sta.lked Infiimriii, we 

 may take the so-called Bell-animalcule ( Yorticelln, fig. 20, C), which 



Yig.2\).—K,Sti:iik>rMulkri. B, VnginicfAa crijstalHna. C, Grou]) of Vcrtlcellai. 

 D, Dctaclied bud of i'orticdla, showin;^ the posterior circlet of cilia. 



may be found in an}' stagnant pool attached to the stems of aijuatic 

 plants. The body in Vorticella forms a kind of cup or "calyx" sup- 

 ported upon a long stalk, which is in turn fixed to some solid object. 

 The stem contains a contractile fibre in its interior, and tlie animal 

 can by this means push itself out or coil itself up with the utmost 

 rapidity. The vibrating filaments or cilia are not scattered over the 

 whole surface of the bell-shaped body, but arc collected to form a 



