Habits o/Anthophysa Mullen. 433 



partly due to its almost incessant activity j for when it is quiet, 

 or nearly so (which happens when food is passing into the 

 mouth), it becomes comparatively quite conspicuous under a 

 one-eighth-of-an-inch objective. It is scarcely as long as the 

 greater diameter of the truncate end of the body. It arises 

 close to the base of the larger cilium ; but whether on the right 

 or left, or nearer or more distant from the mouth than the latter, 

 cannot be said positively. Most frequently it was observed to 

 be flexed in the same direction as its companion ; and occasion- 

 ally it seemed to be quite evident that it was attached nearer to 

 the mouth than the latter. It is highly flexible, and vibrates 

 with great rapidity in what appears to be a gyratory manner. 



The mouth. — This organ is never visible except when food is 

 passing through it. It then may be seen that it lies close to the 

 beak, which acts as a sort of lip by curving over the introcepted 

 particles as they pass into the body. The mouth is highly dis- 

 tensible, at times allowing particles as wide as two-thirds the 

 greater diameter of the body to pass in without any apparent 

 extra effort. It seems undeniable that it possesses discrimina- 

 tive powers in regard to the quality of its food. This one may 

 readily judge of for himself, by seeing the unerring precision 

 with which the particles of floating matter are thrown, by the 

 spasmodic incurvature of the larger flagellura, against the mouth, 

 where, if they are not swallowed, they are detained but for an 

 instant by the smaller cilium, quickly adjudged to be worthless, 

 and then thrown off with a twirl of the organ which held them 

 in temporary abeyance. If, however, the captured morsel prove 

 to be agreeable, the larger cilium assists the operations of the 

 smaller one and the lip, by abruptly bending itself at its point 

 of attachment and laying its basal part across the food and 

 pressing it into the mouth, while the terminal portion is kept in 

 a constant wavy vibration, and curved toward the posterior end 

 of the body. This is usually done in three or four seconds ; and 

 then the cilia return to their usual positions, while the intro- 

 cepted edible passes toward the centre of the body, and is there 

 immediately enclosed in a digestive vacuole. For a while the 

 food dances about in this vacuole with a very lively motion, but 

 finally it subsides into quietude. 



The contractile vesicle. — There is a twofold difficulty in dis- 

 covering the presence of this organ. In the first place, it is com- 

 paratively quite small; and secondly, it pulsates so slowly that 

 it is very rarely possible to see it contract twice in succession 

 between any two of the abrupt lateral deviations of the body 

 which the spasmodic twitching of the arcuate flagellum pro- 

 duces. On this account it has not been possible to determine 

 the precise rate of its systole and diastole. It seems to contract 



