5<D THE PROTOZOA 



dopodia. Here the prey is digested, and the products of digestion 

 find their way by protoplasmic streaming to all parts of the animal. 



In many Mastigophora and Ciliata, the motile organs create a vor- 

 tex current in the region of a well-defined mouth, which usually leads 

 into a distinct pharynx. In some flagellates, the base of the flagel- 

 lum is an area of soft plasm, through which the food particles can be 

 readily engulfed as they strike against it, but in others there is a dis- 

 tinct opening which leads into the endoplasm. In other flagellates 

 (Noctiltica and the Choanoflagellida), a peculiar protoplasmic funnel- 

 shaped collar surrounds the region which answers the same purpose. 

 In most of the Ciliata, the buccal region is surrounded by strong 

 cilia, which are frequently fused to form membranes or membra- 

 nelles ; these send a powerful current of water, containing innutri- 

 tious as well as nutritious particles, toward the mouth, which receives 

 all without discrimination. In some cases, as in certain of the holo- 

 trichous Ciliata, there is a true swallowing or deglutition, by which 

 solid food is gulped into a capacious pharynx and thence into gastric 

 vacuoles. Many of the latter forms have offensive trichocysts, resem- 

 bling the rhabdites of Turbellaria. One of these, upon the approach 

 of its prey (usually a small ciliate or flagellate), launches its darts, 

 which penetrate the cuticle and paralyze the prey. The victim is then 

 swallowed, the mouth of the carnivore enlarging to accommodate it 

 (Fig. 1 8, C). This process is strikingly illustrated by the ciliate 

 Actinobolus radians, which combines the selection of food with the 

 offensive use of trichocysts. This remarkable organism possesses a 

 coating of cilia and protractile tentacles, which may be elongated 

 to a length equal to three times the body-diameter, or withdrawn 

 completely into the body. The ends of the tentacles are loaded with 

 trichocysts (Entz, '83). When at rest (Fig. 19), the mouth is directed 

 downward, and the tentacles are stretched out in all directions, 

 forming a minute forest of plasmic processes, amongst which smaller 

 ciliates, such as Urocentrum, Gastrostyla, etc., or flagellates of all 

 kinds, may become entangled without injury to themselves and 

 without disturbing the Actinobolus or drawing out the fatal darts. 

 When, however, an Halteria grandinella, with its quick and jerky 

 movements, approaches the spot, the carnivore is not so peaceful. 

 The trichocysts are discharged with unerring aim, and the Halteria 

 whirls around in a vigorou's, but vain, effort to escape, then becomes 

 quiet, with cilia outstretched, perfectly paralyzed. The tentacle, 

 with its prey fast attached, is then slowly contracted until the victim 

 is brought to the body, where, by action of the cilia, it is gradually 

 worked around to the mouth and swallowed with one gulp. Within 

 the short time of twenty minutes, I have seen an Actinobolus thus 

 capture and swallow no less than ten Halterias, 



