THE FISH. 83 



under the hinder part of the brain, is the medulla 

 oblongata. 



The hinder, undivided part of the brain is the cere- 

 bellum. 



In front of the cerebellum are the two large, rounded 

 optic lobes, forming the widest part of the brain. 

 In front of the optic lobes are two oval masses which 

 meet in the middle line ; these are the cerebral hemi- 

 spheres, and together they constitute the cerebrum. 

 Observe the olfactory lobes tapering forward in front 

 of the cerebral hemispheres; from these trace the 

 olfactory nerves to the nasal cavities. 



Make a drawing of the brain as seen from above, 

 naming all these parts. Cut open one of the optic 

 lobes and note that it is hollow ; push the eyes out- 

 ward and find a white cord extending inward and 

 backward from each. These are the optic nerves. 



THE MUSCLES OP THE EYE. 



Cut away the upper part of the eye-sockets and find 

 in each a muscle extending outward and backward 

 from the anterior part of the socket to the top of the 

 eyeball. This is the superior oblique muscle. 

 Another muscle coming from the posterior part of the 

 socket will be seen passing forward to be attached 

 under the oblique muscle. This is the superior 

 rectus. Make a drawing showing these muscles. 

 The other eye-muscles may be more easily examined 

 from beneath. 



If the under surface of the skull of the specimen 

 previously studied be not injured, it may be used; 

 otherwise, cut off the head of another fish, and cut 



