50 MANUAL OF ZOOLOGY SECT, i 



of protoplasm, or undulating membranes (it. mb.} in connec- 

 tion with the peristome. These contract so as to pro- 

 duce a wave-like movement which aids in the ingestion 

 of food. 



The tentacles, which, in the Tentaculifera (Fig. 20), take 

 the place of cilia in the adult, are elongated cylindrical 

 structures, capable of protrusion and retraction, and having 

 the distal end expanded into a sucker. The tentacle is 

 practically tubular, the core consisting of a semi-fluid proto- 

 plasm, while the outer part is tolerably firm. Infusoria and 

 other organisms are caught by the tentacles, the cuticle of 

 the prey is pierced or dissolved where the sucker touches 

 it, and the semi-fluid protoplasm can then be seen flowing 

 down the tentacle into the body of the captor. A single 

 tentacle alone may be present (3\ or the tentacle may be 

 branched (4), the extremity of each of the branches being 

 suctorial. In some forms (o), the tentacles are devoid of 

 sucker-like extremities, and can be moved about actively to 

 catch the prey. 



The meganucleus is often ovoid as in Paramcecium. In 

 other cases it may be long and band-like (Fig. 19, 3, 

 mg. .), horseshoe-shaped (#), very long and constricted 

 at intervals so as to look like a string of beads, or 

 branched. In nearly all cases one or more micronuclei 

 are present. In Vorticella and others there is a single 

 contractile vacuole which opens, as in Euglena, through 

 the intermediation of a reservoir into the gullet. In other 

 Infusoria there may be one, two, or many contractile vacu- 

 oles. In some instances the protoplasm is hollowed out 

 by numerous non-contractile vacuoles. Trichocysts mainly 

 occur in the forms with a uniform coating of cilia : more 

 complicated bodies of similar character termed nematocysts 

 (9, c) occur in some cases. 



