CENTERS OF CORRELATION. 



255 



ventricle is much thicker than the rest and is known as the collic- 

 ular region. The portion which roofs over the optic ventricle 



:omm. ansulata Cereb.ped 



Fig. 127. — Outline transverse sections through the mesencephalon of various 

 vertebrates to illustrate the changes of form of the tectal region. A, a cyclostome; 

 B, a selachian; C, a ganoid; D, a bony fish; E, an amphibian; F, man (after 

 Koelliker). r, nucleus ruber; 5. n., substantia nigra. 



is known as the tectum opticum. (It must be remembered always 

 that the tectum opticum is only a part of the tectum mesencephali.) 



