WHEEL-BEARERS. 231 



all; for the lips appear to possess the sense of taste, or of 

 some modification of touch, which enables them to refuse 

 or to receive the atoms presented to them, so that only 

 such particles pass down the throat as are selected for 

 food. Some of the atoms of pigment are admitted, and 

 one of the most pleasing sights connected with these 

 animals, is to watch the swallowing of coloured food, its 

 reception into the singular sunken mouth, where the 

 great powerful jaws act upon it: thence its dismissal 

 through the gullet, where certain glands pour upon it 

 their secretions, into the stomach, where other glands, 

 answering to a liver, change it ; and thence into the 

 intestine and rectum, until its indigestible portion is 

 discharged through the cloacal orifice. 



The object of the mingling of colour Avith the water in 

 which these and similar animals are held for observation, 

 was the tracing of the phenomena of digestion. And, 

 indeed, it renders the whole process beautifully distinct; 

 for, from the transparency of the tissues, the presence 

 of the coloured pellet is everywhere recognizable, since 

 it retains its form and hue under all its changes, clearly 

 revealing to us the shape, dimensions, and directions of 

 the various canals through which it passes; here and 

 there diffusing throughout the viscus in which it is held 

 a beautiful roseate hue, more or less deep, without, how- 

 ever, causing- it to lose its own definite outline. 



Let me now direct your attention to the organs devoted 

 to the seizing and mastication of the food. And the 

 more, because the form of these organs in the Rotifera is 

 quite peculiar, quite unlike what is found in any other 

 class of animals; though the parts are essentially the 

 same as those which we have already seen entering into 

 the mouth in insects. 



Removing the carmine-stained water, I put into the 

 live-box a drop from a vase very rich in organisms of 

 many kinds. Among these you see very numerous the 



