126 GENERAL BIOLOGY. 



(ff) At each side of the fourth ventricle 

 are the peduncles of the cerebel- 

 lum. 

 (d) Cut off the dorsal wall of one optic lobe 



and see its ventricle. 



(e) Make a median (vertical) longitudinal sec- 

 tion of the brain and see the continuity 

 of the third and fourth ventricles. 

 Diagram! 



VI. The eye. 



Divide one into two lateral halves, and the other 



into anterior and posterior halves. 

 Observe : 



1. The two humors. 



2. The sclerotic coat. 



3. The choroid coat. 



4. The retina. 



5. The ora serrata. 



6. The entrance of the optic nerve. 



7. The pecten. 



8. The ciliary processes. 



9. The lens. 



10. The iris. 



11. The pupil. 



VII. The Feather. 



In a tail feather, note : 

 1. The stem (scapus), consisting of : 



(a) The quill (calamus), the hollow proximal 

 part. 



