192 



C. Judson Herrick 



formis which discharge their highly elaborated nervous impulses into the 

 hippocampus. 



There is no área in the amphibian hemisphere which can be regarded 

 as primordial general cortex, or neopallium. The physiological connec- 

 tions which would opérate in the differentiation of such an área are pre- 

 sent in the lateral wall, but they have not emerged in definite morpholo- 

 gical patterns. 



Our interpretation of these facts is that the Amphibia were derived 

 from an extinct ganoidean ancestor in which the dorsal and lateral olfac- 



a.pl.d 



.p. hip. 



setítum 



32 



f.rhed.t. 



sa.v. 



I-"ig. 2,2. — Section similar to the last taken ¡nmediately in front of the foramen 



interventriculare. 



tory áreas were not so clearly separated as they are in the living fishes 

 which have been considered in this contribution. The dorsal portion of 

 the common área olfactoria dorso-lateralis which, in the course of the 

 evagination of the hemisphere, comes to lie in its medial wall was dif- 

 ferentiated as primordium hippocampi. Its ventral portion becomes the 

 lateral wall of the hemisphere, throughout which are made all of the con- 

 nections of the lateral forebrain bundle. These connections include those 

 of the olfactory projection tract (tractus pallii) and the ascending and 

 descending somatic projection fibers connected with the thalamus. This 

 is the urodele condition. Only in Anura are dorso-lateral and ventro-la- 

 teral quadrants clearly separated, thus defining lobus pyriformis above 

 and strio-amygdaloid complex below. 



