PHYSIOLOGY OF THE INVERTEBRATA. 377 



evidently arises from the complete flexibility of the flagella, 

 by which a propelling motion plainly could not be ap- 

 plied." 



The diameter of the flagellum of some forms is only 

 0.00000488526 or the ^irm^ of an inch.* 



In the Ciliata, the outer surface of the body is provided 

 ■with vibratile cilia. These are organs of locomotion, touch, 

 and prehension; and they may also aid in the function 

 of respiration by causing a renewal of the water, which 

 furnishes the necessary air for the function of respiration. 



The cilia of these animals are homogeneous structures con- 

 tinuous with the ectosarc. 



The Ciliata are divided as follows — 



As already stated certain Infusoria have a portion of the 

 protoplasm differentiated, so as to suggest a body comparable 

 to the muscular fibres of the higher animals. This filament, 

 or myophane, occurs in the peduncle of the Vorticellce ; and it 

 is by this means that the stalk or peduncle is capable of 

 forming a spiral, when the animal is disturbed. 



* See the paper by the Eev. W. H. Dallinger, F.R.S., in the Transactions 

 o/tlie Hoyal Microscopical Society, 1878, p. 174. 



