THE COD. 123 



vestibule (r) and of the three semicircular canals : the latter have 

 the usual arrangement; the anterior (a.s.c) and posterior (p.s.c) canals 

 have their adjacent limbs confluent, so that the two canals open by three 

 apertures into the vestibule ; the horizontal canal (h.s.c) lies entirely to 

 the outer side of the vestibule, into which it opens by two separate aper- 

 tures, and the ampullx (a) are situated at the actual extremities of the 

 canals, those of the anterior and horizontal canals being anterior, 

 that of the posterior canal posterior. 



183. The two otoliths, one large (s) and shaped something like a 

 shell (sagitta), and the other very small (at) (asteriscus) lying in a small 

 diverticulum of the vestibule, just beneath the ampulla of the posterior 

 canal. 



G..S.C 



8 



FIG. 33. Gadus morrhua. The organ of hearing. (From a 

 sketch by Mr. G. B. Howes.) 



z/, vestibule: a.s.c, anterior, p.s.c, posterior, and h s.c, horizontal, 

 semicircular canals : a, a, a, ampullae: s, sagitta : as, asteriscus. 



XXXVI. Examine the brain : if a fresh fish is used for 

 the purpose and no spirit-specimen is available, 

 the verification of the characters of the ventral 

 surface must be left until the origins of the nerves 

 have been made out, when the brain may be 

 removed : note the following : 



184. The medulla oblongata (Fig. 34, m.o\ or hind- 

 most division of the brain, continuous with, and of scarcely 

 greater diameter than, the spinal cord. 



