Functional factors in the morphf)louy f)f the forebrain of fishcs i()i* 



missura anterior. From the external sulcus formed by the eversión of 

 the área dorsahs (ñg. 23) it extends inward into contact with the área 

 medialis below the área dorsalis. It is accompanied by the strong tractus 

 olfactorius lateralis, from which it receives fibers derived from the bulbus 

 olfactorius. This área appears not to have been recognized in the carp by 

 Sheldon (his nucleus olfactorius lateralis is a part of the área olfactoria 

 dorsalis of this description). In his figures 38 and 56 there is an unnamed 



hab. 



.a. ol. d'. 



com. hab 



troi.lat. 

 tr. ol. m 



tf. oal. 



\ nuc. po. 



f. rned t. 



hyth. 



20 



Fig. 20. — Diagrammatic median section of the brain of Amia calva. The outline 

 is based on figure i of fohnston (191 1 a). The courses of some of the longitudinal 

 fiber tracts are indicated from the descriptions of Johnston and others. The 

 positions of the área somática and the área olfacto-somatica are indicated as 

 projected upon the medial surface. 



nucleus internal to the <' nucleus taeniae» which corresponds probably 

 with Johnston's nucleus olfactorius lateralis of Amia (fig. 24, a. ol. 1). 



4. Área olfacto-somatica. — The ventral limits of the área olfactoria 

 dorsalis are clearly defined medially and laterally, but in the intermedíate 

 región there is a transitional territory between the lower border of this 

 área and the área olfactoria lateralis whose structure and connections in 

 teleosts (figs. 23, 24, a. ol. s.) show that it is comparable with the área olfac- 

 to-somatica of Acipenser (figs. 3, 4). It was termed palaeostriatum by 

 Sheldon and is probably an undifferentiated olfacto-striatal primordium. 



