VERTEBRATES WITHOUT JAWS 



opt.L. 



IV. 9 



cer. 



hi/pot. 



Fore. 

 cerh. h. 



Mid- Hind- brain. 



opt.L med. c ^ or 



Fore. - Mid- Hind- brain. 



Lam.i 



Fore. 



Mid. 



Hind — brain. 



Fig. 64. Brain of the lamprey. 



A, side view; B, dorsal view with choroid plexus intact; c, after removal of choroid, cereb. 

 cerebellum; cer. h. cerebral hemisphere; chor. choroid plexus; hypot. hypothalamus; it. iter 

 between third and fourth ventricles; lam.t. lamina terminalis (thickened anterior wall of 

 third ventricle); med. medulla oblongata; opt.L optic lobe; pin. pineal eye; thai, thalamus; 

 3rd v., 4th v., third and fourth ventricles. (After Sterzi.) 



a number of very large Miiller's fibres, originating from giant cells in 

 the reticular formation of the brain, whose large dendrites (Fig. 65) 

 receive fibres from several higher centres, providing an uncrossed final 

 common pathway to the spinal cord. There is some difference of 

 opinion as to whether any branches of these large fibres proceed 



