ioo Vertebrata. 



molluscs, they require to take in very large quantities 

 of this material for their nourishment, which they do 

 in the following way. The jaw arches are covered all 

 around their edges with horny plates of ' whalebone/ 

 fringed with bristles in place cf teeth, and these act 

 as strainers. In feeding, the animal opening its mouth, 

 takes in a mouthful of sea-water and its animal 



FIG. 48. 



Head and tongue of whale. 

 a, tongue (represented much too large) ; b, whalebone plates. 



contents, and then by closing the jaws and pressing 

 the tongue against the palate, expels the water through 

 the slits between the whalebone plates, which by their 

 opposition and by their bristly margin retain the solid 

 materials to be subsequently swallowed. 



In some whales there are exceedingly minute 

 rudiments of the hind limbs, in the form of small 

 ischia or pelvic bones, embedded in the muscles of 

 the abdomen, and not visible on the surface. 



Whales have usually complex stomachs, often 

 with four chambers; they have also a moderately long 

 alimentary canal, large and tortuous networks of blood- 

 vessels along the ribs, and a thick fleshy diaphragm. 



