160 ANIMAL PHYSIOLOGY. [LESSON 46. 



malcules) for the supply of the animal's wants. To obtain this food 

 from the strong stream of water constantly being propelled through 

 its interior, the mouth has need of a special arrangement of ciliated 

 processes, which are found accordingly. The funnel-shaped pharynx 

 (b) is well shown in this view, and leads to the oesophagus (c) ; as 

 before, the biliary follicles (d) obscure the stomach. The reverse 

 side of this preparation (Fig. 258) shows the stomach (c?), and the 

 whole of the short intestinal canal (5), the mouth (a), and the 

 biliary follicles (c). 



FIG. 258. FIG. 



Back view of alimentary canal, T. 



Australia. The arms of T. Australis. 



Another preparation has been copied, to show the disposition of 

 the unmutilated arms, with their central one curled, and all of them 

 armed with remarkably strong cilia (Fig. 259). These are addition- 

 ally supported by a pair of strong calcareous (carbonate of lime) 

 bones, which are placed on either side, lying between a double mem- 

 brane, and just within the margin of the strong cilia. 



The aperture at the upper portion of the figure passed around 

 the oasophagus, which had to be dissected out of it. The nervous 

 ring which surrounds the 03sophagus, and distributes branches to the 

 arms, is found in this situation. 



LESSON XLYI. 



NUTRITION IN THE LAMELLIBKANCHIATA, AND IN THE PTEROPODA. 



702. In the common Oyster, the visceral mass occupies about 

 half the cavity of the shell next the hinge. The rest of the space be- 



