of four Vertebrates. 



PI. IT. 



FIG*. (7, A , #. P, anterior cerebral hemispheres ; z, optic thalami ; w, tubercula quadri- 

 gemina; ^cerebellum; w, pons Varolii; r, spinal cord; w, spine; , tail; a, eyes 

 n, nose ; o, ear; tj, # 2 , * 8 , visceral arches ; bv, anterior eitreraU^;;^, posterior ,ex ;< ^ 

 tremity. (Haeckel.) , * 2 



