Functional factors in the morphology of the forcbrain of fishcs 171 



matic projection tract (fig. 20). These two systems are important com- 

 ponents of the lateral forebrain bundle of Amphibia. 



This account of Amia is based on Johnston's descriptions. In the carp 

 Sheldon (1912, p. 238) recognized the presence of this área but did not 

 efíect its analysis. It includes the nucleus entopeduncularis and perhaps 

 some others. Holmgren's account also is very incomplete. The fiber 

 tracts connected with the feebly developed área somática of teleosts are 

 not well known. Holmgren describes connections of this región which 

 he regards as comparable with the somatic projection tract described by 

 johnston in ganoids, 



Fiber tracts of Teleostorni. — The functional connections of the parts 

 of the forebrain in the higher members of this group are in principie the 



^.ol. d. dm. 



,-a.o( s. 



a. 01. t. 



a.ol.d. I. 

 \^' y" ''■■-■■ _/' 



a.oifTi. ,^ 

 v.c 



23 



Fig. 23. — Diagrammatic transverse section through the telencephalon médium 

 of adult Amia calva immediately in front of the commissura anterior. Based on 



Kappers and Johnston. 



same as in the more generalized types already described, but these brains 

 are far more highly specialized with corresponding complexity of struc- 

 ture and the greatest diversity of detall in the various species. By reason 

 of thé difference in nomenclature employed in the published descriptions 

 and the fragmentary character of many of the observations it is very dif- 

 ficult to make successful comparisons of the different species and to de- 

 termine the fundamental features which they have in common. The 

 connections here enumerated probably exist in all of the Teleostomi. 

 Only certain ones of the longitudinal conduction paths are mentioned. 

 There is in addition a bewildering complexity of shorter connections, 

 decussations and commissures. 



The tractus olfactorius of Amia shows a tendency to divide into me- 

 dial and lateral tracts and the same is true in teleosts generally; but the 



