Functional factors in thc morpholoí^}' oí the forcbrain of fishf> 107 



TIVE ENOBRAIN 

 «ION VENTRICLE 



The brains of Amia and various Teleostei have been described by 

 many writers and some of these descriptions are very complete. The 

 nomenclature employed and the interpretations of these authors are very 

 diverse and no attempt will be made here to summarize this Hterature. 

 The most complete recent accounts have been given by Catois ( 1901, se- 

 veral teleosts), Goldstein (1905, several 

 teleosts), Kappers (1906, Gadus, Lo- 

 phius, and 1907, Amia, Lepidosteus), 

 Sheldon (1912, Cyprinus carpió), Johns- 

 ton (191 1 a, 1912 a, Amia, Acipen- 

 ser, Polyodon, Lepidosteus, Ameiurus), 

 Hoimgren (1920, Osmerus and other 

 teleosts). The conclusions whicli are 

 here summarized are based on a study 

 of this Hterature and personal observa- 

 tions. The subdivisions of the telence- 

 phalon médium will now be briefly re- 

 viewed, basing the account on Amia 

 calva, supplemented by the published 

 descriptions of the fiber connections of 

 various l'eleostei. 



1. Área olj actor ia medialis. — This 

 subdivisión is in most species of modera- 

 te size and is arranged as ¡n Acipenser 

 (figures 20, 23, 24), extending from the 

 base of the bulbus olfactorius backward 

 to the commissura anterior. It is sepa- 

 rated from the overlying área dorsalis by 



a cell-free zona limitans and a more or less evident ventricular sulcus. It 

 is continuóos behind with the nucleus preopticus, which lies between 

 commissura anterior and chiasma opticum, and the latter nucleus is con- 

 tinuous with the hypothalamus. Tiiese áreas contain various special nu- 

 clei, whose arrangement need not be further considered here. 



2. Área olfactoria dorsalis. — This includes the epistriatum, nucleus 

 olíactorius lateralis and nucleus laeniae of Kappers (1907) or pars pallialis 

 (1921), the primordium hippocampi of Johnston (1911 a), the nucleus 

 olfactorius dorsalis, nucleus olfactorius lateralis, nucleus pyriformis and 



Fig. 19. — r>¡agr<'immatic longitu- 

 dinal section throiigh the fore- 

 brain of a teleost. As in the stur- 

 geon (fig. I ), the true evaginated 

 cerel)ral hemispheres contain 

 only tile olfactory bulbs, below 

 which there are great thickenings 

 of thc unevaginated primitive 

 endbrain, which arise first em- 

 bryologically in the side walls, as 

 in the -sturgeon, but in the adult 

 are attached only to the floor. 

 Conventional markings as in 

 figures I, 7 and i:?. 



