178 RALPH EDWARD SHELDON 
ce. Diencephalieg connections =. 4-0-0)... ase eee 214 
(1) . Tractus olfacto-shabenulariss. =). 9442-5 72 214 
(2)? (Fascreultismretroflexuss: 45 jt. oo eee 217 
(3) Tractus habenulo-diencephalicus..................... 217 
(4) Posthabenular preoptic connections. ................. 218 
(5)... Epiphysealiftbers’: co. ).)....'. Uae eee eee 218 
(6) Fasciculus medialis hemisphaerii..................... 219 
(7) Fasciculus lateralis hemisphaerii..................... 222 
(8) The nucleus preopticus and its connections........... 227 
5. The conduction pathways tron... 6.00.5 ic eee ee ee 231 
6. The morphological areas of the forebrains)... . {.....024- sone 238 
LED. Discussionyy.2 Sere. 5 2 eRe ee otc Le A alk Are to) 
TVs: Literature icrtedseon: |.) 6.8 eee ee seh thee gh evened a 248 
Vio, eres: Oe ete Bie Mc. ok SRI N cane occ Se 254 
I. INTRODUCTION 
The information here added to that heretofore existing in the 
literature is derived largely from a study of the olfactory apparatus 
in the carp, Cyprinus carpio (L). The olfactory apparatus is 
highly developed in the eyprinoids which, therefore, lend them- 
selves readily to its study. For the elucidation of difficult points, 
however, comparison has been made with Weigert and Golgi 
sections of the brains of the pike, Lucius lucius (L), the gold- 
fish, Carassius auratus (L) and the catfish, Ameiurus nebulosus 
(Le Sueur). 
I am indebted to Prof. C. Judson Herrick for helpful sugges- 
tions and criticism in every phase of the work, together with the 
opportunity to use his unexcelled neurological library and his 
personal material. Prof. R. R. Bensley likewise placed at my 
disposal all the facilities of the department, including the services 
of the artist, Miss Katharine Hill, who has drawn, with the most 
painstaking care, the larger portion of the figures. Through the 
kindness of Prof. Charles Brookover, of Buchtel College I have 
been able to examine preparations of the brain of Amia calva and 
to secure well preserved material for most of the Ramén y Cajal 
impregnations. Acknowledgments should also be made to Prof. 
B. G. Wilder of Cornell University, at whose suggestion this re- 
search was undertaken, and to Prof. 8. H. Gage of Cornell Uni- 
versity and Prof. FE. L. Mark of Harvard University, in whose 
laboratories important parts of this investigation were conducted. 
