368 JULIA ELEANOR MOODY 



prey, but because of the presence of trichocysts at their tips, 

 he looked upon them as organs of protection. 



In 1901 in his paper dealing with some interesting protozoa 

 found in Van Cortlandt Park, Calkins records his observations 

 on the feeding habits of Actinobolus and the functions of the 

 tentacles. To quote: ('016, p. 50) 



This remarkable organism possesses a coating of cilia and retractile 

 tentacles which may be elongated to a length equal to three times the 

 diameter of the body, or withdrawn completely into the body. The 

 ends of the tentacles are loaded with trichocysts (Entz '83). When 

 at rest the mouth is directed downward and the tentacles are stretched 

 out in all directions forming a minute forest of plasmic processes, among 

 which smaller ciliates such as Urocentrum, Gastrostyla etc., or flagel- 

 lates 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 jerky move- 

 ments, approaches the spot, the carnivore is not so peaceful. The 

 trichocysts are discharged with unerring aim and the Halteria w^hirls 

 around in a vigorous but vain effort to escape, then becomes quiet, 

 with cilia outstretched, perfectly paralyzed. The tentacle with the 

 the prey fast attached is then slowly contracted until the victim is 

 brought to the body, where by the 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 Actinobolus capture and 

 swallow no less than ten Halterias. 



Thirty-five years, therefore, after its discovery by Stein in 

 1867, Calkins solved the problem of the function of the ten- 

 tacles of Actinobolus, finding that, contrary to the conclusion 

 of Entz, it is a holozoic form, existing exclusively on the small 

 ciliate, Halteria. 



2. Material and method 



The pond water in which Actinobolus was found was brought 

 to the laboratory from Van Cortlandt Park. Entz's obser- 

 vation, unverified, by Von Erlanger, that the ciliate is always 

 found associated with suctorian forms, was not found to be crue 

 in this case, other ciliates and flagellates abounding, but no suc- 

 toria. Entz's statement may be accounted for by the fact that 

 Actinobolus bears a superficial resemblance to the suctorian 

 Sphaerophrya and when at rest might easily be mistaken for 

 this form. 



