2 GO EVENINGS AT THE MICROSCOPE. 



are riclilj covered witli cilia. A certain portion of tlio 

 atoms are thus arrested bj these cilia, and are hurled 

 by their vibrations down this gulf. Yet not all, nor 

 nearly all ; for the lips appear to possess the sense of 

 taste, or of some modification of touch, which enables 

 them to refuse or 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 col- 

 oured 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 in- 

 digestible portion is discharged through the cloaca! 

 orifice. 



The object of the iningliDg of colour with the water 

 in which these and similar animals are held for obser- 

 vation, was the tracing of the phenomena of digestion. 

 And, indeed, it renders the whole j)rocess beautifully 

 distinct ; for, from the transparency of the tissues, the 

 presence of the coloured pellet is everywhere recognis- 

 able, 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 diftnsing throughout the vis- 

 •cus in which it is held a beautiful roseate hue, more 

 or less deep, without, however, losing its own definite 

 outline. 



Let me now direct your attention to the organs de- 

 voted to the seizing: and mastication of the food. And 



