158 



ANIMAL PHYSIOLOGY. 



[LESSON 45. 



join, and form a transverse fringed band above the mouth ; the bent 

 portions of the fringed arms are supported by slender, elastic, calca- 

 reous processes. 



700. A figure of the nutrimental organs in situ is given (Fig. 

 FIG. 255 A. 255). The peduncle (e) for attachment is 



seen in connection with that layer of the 

 mantle that forms the back ; a double heart 

 is said to exist in these animals, the auricles 

 of which (b, b) are placed on either side of 

 the alimentary canal, and above the point 

 of junction of the curled arms. It is, how- 

 ever, most probable that the so-called " hearts" 

 are simply the external openings of the 

 ovaria, by which the ripe ova effect their 

 escape. The stomach is entirely concealed 



FIG. 255. 



Lingula, natural size. Nutrimental organs in situ, T. Australia. 



by a mass of biliary follicles (c), which completely cover it ; above, 

 it is covered with peritoneum. The intestine (d), which takes an 

 oblique direction, is not very conspicuous, owing to its depth ; two 

 of the arms, fringed with strong cilia (a), are seen on either side, and 

 in front the remains of the third arm (a), the curl having been cut 

 off, to show the other parts of the structure. Another, a side view 

 of Terebratula Australis, is given in Fig. 256; here the right 

 (lower) arm is partly seen, being concealed by the great curl usually 



