68 INFUSORIA. 



the anterior extremity of the body, their termina- 

 tions only being capable of performing vibratory 

 movements. But there is reason to infer that 

 many of the organisms in which they occur are, in 

 all probability, members of the vegetable king- 

 dom. 



All the above appendages are properly to be 

 regarded as elongated processes of the cuticular 

 layer. It has been asserted by some observers 

 that each of the cilia arises from the apex of a 

 four-sided prism. But further observation on this 

 point is necessary. 



The contractile movements which the stalk of 

 Vortioella undergoes have been described in our 

 account of that Infusorium. 



II. BovclopiBient. — Propagation is effected 

 among the Infusoria by 



a. Fission, 

 h. Gremmation, 



c. Encystation, and 



d. True reproduction (i. e. by ova and sper- 



matozoa) ? 



Of these the three first tend to separate the 

 individual into a number of seemingly independ- 

 ent beings or ' zooids,' while the fourth method 

 gives rise to new individuals. For an individual 

 (in Zoology) is equal to *'the total result of the 

 development of a simple ovum." 



a. Multiplication by the method of fissipa- 

 rous division is of frequent occurrence. It may 

 be either longitudinal (Vorticella), or transverse 

 (Stentor), or either indifferently {Chilodon, Eu- 

 plotes, Parameciuni). It is usually stated that 



