Functional factors in thc morphology of the forcbrain of fishes 191 



and the ventro-lateral (juadranl, for these are in very intimate functional 

 association. In Anura these two quadrants are sharply separated by 

 limiting sulci and a cell-free zona liniitans. The dorso-lateral quadrant 

 is primordial lobus pyriformis; the ventro-lateral quadrant is the amyg- 

 dalo-striate complex. 



The dorso-lateral quadrant appears to occupy an ambiguous position. 

 If derived from the ventral part of the área olfactoria dorsalis of generaii- 

 zed fishes, it has taken over the greater part of the secondary olfactory 



p-hip. 



-lob.p. 



Fig. 31. — Transversa section through the cerebral hemispheres of adult Am- 



blystoma tigrinum at the level of the foramen interventriculare. The conventional 



markings on the left side illustrate the author's view of the subdivisions of the 



área olfactoria in comparison with fishes. 



connections and all of the tractus pallii conections of the área dorsalis 

 and to these it has added termináis of somatic projection fibers ascending 

 from the thalamus which in fishes do not reach the área dorsalis at all. 

 If derived from the área olfactoria lateralis of fishes (for which strong 

 evidence can be adduced) it has usurped the tractus pallii connections of 

 the área dorsalis. Upon either of these hypotheses this detachment of 

 the olfactory projection tract from the primordium hippocampi mav 

 have been an important factor in giving to the hippocampus its higher 

 physiolgical rank as an associational mechanism in the hierarchy of cor- 

 tical centers. For, in the mammals, as Ramón y Caja! has shown, there 

 are very extensiva mechanisms of cortical correlation in the lobus pyri- 



