102 THE VITAL FUNCTIONS. 



Hydatid, for instance, has four sucking apertures 

 disposed around what may be called its head : the 

 Tcenia has oral orifices in each of its jointed seg- 

 ments: but the higher entozoa, as the ^.9cam, have 

 a single mouth. In the Annelida, the margin of 

 the mouth is often divided, so as to compose lips ; 

 of these there are generally two, but in the Leech 

 there are three. 



When the instrument for suction extends for 

 some length from the mouth, it is generally termed 

 a proboscis : such is the apparatus of the butterfly, 

 the moth, the gnat, the house-fly, and other insects 

 that subsist on fluid aliment. The proboscis of the 



Lepidoptera, (Fig. 266), is a 

 double tube, constructed by the 

 two edges being rolled longitudi- 

 nally till they meet in the middle 

 of the lower surface ; thus form- 

 ing a tube on each side, but 

 leaving also another tube, inter- 

 mediate to the two lateral ones. 

 This middle tube is formed by 

 the junction of two grooves, 

 which, by the aid of a curious apparatus of hooks, 

 resembling those of the laminae of a feather already 

 described, lock into each other, and can be either 

 united into an air tight canal, or be instantly sepa- 

 rated at the pleasure of the animal. Reaumur 



are not perforated, and do not perform the office of mouths; and 

 the true mouth for the reception of food is single. Cuvier discovered 

 an animal of this class furnished with above a hundred of these cup- 

 shaped sucking organs. See Edinburgh Philos. Journal, xx, 101. 

 The Sipunculns, among the Echinodermata, has a long protractile 

 tube for the purpose of suction. 



