164 



.RECEPTION OF SOLID AND LIQUID ALIMENT. 



of Insects, of which a pair is attached to each jaw (fig. 84); 

 the tentacula of Mollusks, which are sometimes extremely 

 prolonged, as in the Cuttle-fish tribe (fig. 85); and the 

 similar organs of the polypes (fig. 71). 



Fig. 84. JAWS OF THE 

 SAME INSECT. 



Fig. 85. LOLIGOPSIS. 



173. The reception of liquids is accomplished in two ways. 

 Sometimes the liquid is made to fall into the mouth, simply 

 by its own weight (fig. 86) ; in other instances it is drawn or 

 pumped up into this cavity, either by the expansion of the 

 chest, which causes a rush of air towards the lungs, or by 

 the movement of the tongue, which, being drawn back like a 

 piston, produces the action of sucking. Some of the lower 

 animals are destined to be entirely supported by liquids which 

 they find in plants, or which they draw from the bodies of 

 other animals whereon they live as parasites. This is the 

 case with many Insects ; and their mouth, instead of present- 

 ing the ordinary structure, is formed into a sort of tube or 

 trunk, very much extended, through which the juices are 

 drawn up according to the wants of the animal. Such a 

 conformation exists in the butterfly and moth tribe, whose 



