CENTERS OF CORRELATION. 



257 



corpora quadrigemina. It is probable that the roof in amphibia 

 is an indifferent center for cutaneous, auditory and optic stimuli 

 in which special centers for optic and auditory tracts are beginning 



Fig. 12S. — Transverse section of the diencephalon of the rat at the level of the 

 body of Luys. From Cajal (Textura, etc.)- A, optic tract; Sand C, nuclei of the 

 corpus geniculatum laterale; D, sensory nucleus (end nucleus of lemniscus); E, 

 nucleus of Luys; F, zona incerta; I, posterior commissure; N, nucleus triangularis. 



to be formed. In its caudal part the roof is comparable to the 

 coUiculus of fishes rather than to the tectum opticum; in its cep- 

 halic part the reverse is true. 



The form of the midbrain roof in reptiles and mammals is in 

 17 



