58 INFUSORIA. 



sel. The latter then quits the alimentary appa- 

 ratus and is passed into the interior of the body, 

 to the posterior extremity of which it runs, and 

 then, turning upwards, rises on that side which is 

 opposite the pharynx. For some time after the 

 morsel has passed from the pharynx it retains 

 the fusiform shape which it had acquired therein, 

 but when, changing its course, it commences to 

 turn upwards, it becomes somewhat globular in 

 form. As soon as this is the case it ceases to have 

 an}^ separate motion of its own, and takes part in 

 a general rotatory movement which is shared by 

 the entire contents of the interior of the body, 

 the nucleus alone (according to Lachmann) being 

 exempted. The morsel, after making one or 

 more circuits within the body, at length arrives 

 in the neighbourhood of the anus through which 

 it passes into the vestibulum. The final removal 

 of the indigestible remains of the food is effected 

 by means of the strong non-vibratile cilia which 

 arise in front of the mouth, and it is not improba- 

 ble that these (which must not be confounded 

 with the vibratile cilia belonging to the spiral) are 

 also employed in guarding the commencement 

 of the alimentary apparatus from the ingress 

 of coarse or adventitious particles, which might 

 otherwise obstruct the entrance of the oesophagus. 

 Though usually fixed, the Vorticella is some- 

 times observed to detach itself and swim slowly 

 about in the surrounding water ; it has also the 

 power, when alarmed, of contracting its stalk into 

 a series of spiral folds, and of again causing it to 

 resume its erect position, both of these movements 

 being performed with great rapidity. 



