THE INFUSORIA 



467 



takel ") of this type are always present. In the genus Ephdota 

 there are present in addition prehensile tentacles (" Greiftentakel "), 

 which end in a fine point. The exterior of the tentacle is clothed 

 by a delicate pellicle, continuous with that of the body, and forming 

 in the suctorial tentacles a sheath or tube, from the end of which 

 the sucker protrudes. The tentacles are slowly retractile. When 

 expanded they appear homogeneous ; but in the process of retrac- 

 tion they exhibit a spiral marking, due apparently to creases and 

 folds in the pellicle, and not to be interpreted as indicating the 

 presence of myonemes. The tentacles are used for the capture of 

 prey, which consists chiefly of ciliates. As soon as the sucker-like 

 extremity of a tentacle touches a ciliate it is held fast ; the substance 

 of the prey is then 

 slowly absorbed by the 

 tentacle, and passes as 

 a stream of granules 

 down the axis of the 

 tentacle. During this 

 process the ciliate re- 

 mains alive, with cilia 

 movin gand contractile 

 vacuoles pulsating, until 

 about half its substance 

 is absorbed (Filipjev). 



In the genus Rhyn- 

 cheta there is but a 

 single tentacle of great 

 length ; in Urnula (Fig. 

 191), one or two. Other 

 genera bear usually 

 many tentacles, which 

 may be distributed 

 evenly over the body- 

 surface, or, more commonly, occur in special regions of the body 

 or are distributed in tufts and patches. In Dendrocometes the 

 tentacles occur in bunches borne on branches or arm-like processes 

 of the body-wall. 



Ishikawa describes in the larger prehensile tentacles of Ephdota buetschliana 

 a system of filaments, consisting of fine threads running parallel to one 

 another in pairs and continued into the body as far as its base. The filaments 

 stain deeply with iron-haematoxylin. According to Collin (877), each such pair 

 of filaments is in reality the optical section of a fine tube. A suctorial tentacle, 

 according to Collin, represents a deep invagination of the ectoplasm, opening 

 at its innermost end into the endoplasm like the cytopharynx of a ciliate. 

 The prehensile tentacles, on the other hand, are special formations of a 

 different kind, simple evaginations of the body-wall, pseudopodial in nature, 

 and containing from one to three axial filaments, the number increasing with 

 the age of the tentacle. 



FIG. 191. Urnvla epistylidis, epizoic on Dendro- 

 soma radians. A, B, Individuals with one or two 

 tentacles respectively ; O, formation of a bud 

 (g) ; D, the "same seen in transverse section 

 passing through the bud and the macronucleus 

 of the parent ; E, free-swimming larva ; jP, en- 

 larged view of the single tentacle, showing the 

 spiral striation. After Hickson and Wads- 

 worth (886). 



