&IGH SCHOOL ZOOLOGY. 



25& 



of the nettling-organs of the Ccelenterates. Two functions are 

 discharged bj the cilia ; they bring food towards the mouth, and 

 they serve for locomotion, but the contractile ectoplasm assists 

 in the latter function. Two contractile vacuoles are present in 

 this genus, which discharge their contents by radial tubes. 

 Within the diffluent endoplasm may be seen food-particles cir- 

 culating, which are being subjected to its digestive action ; the 

 nucleus is also situated there. This organ is peculiar in the 



Fig. 193. — Types of Ciliated and Suctorial Infusoria. 



1, ParaiuflDciuui ; 2, Opalina ; 3, Stentor ; 4, Onj-ehodromus ; 5, Vorticella ; 

 6, Acineta ; c«. contractile vacuole ; /;(, mouth ; v, \x'stil)ule, leading towards mouth ; 

 n, nucleus ; t, trichocysts ; a, anus ; /, contractile fibre in stalk ; r, cilia of "right" 

 border. 



Ciliata and presents many varieties of form (Fig. 193) ; it con- 

 sists of two pai'ts, a larger and a smaller (tlie nucleus and the 

 micronucleus) ; both of these play an important part in the 

 method of multijilication by fission, which is so common in this 

 group. They are also active in conjugation, a method of repro- 

 duction which occurs in other groups of Protozoa as well as in 

 the Algse. 



22. The trumpet-animalcule {Stentor) may be taken as an ex- 

 ample of another order (Heterotricha) where the cilia which 



