664 C. JUDSON HERRICK AND JE ANNETTE B. OBENCHAIN 



yet undetermined, and the first step in the solution of this prob- 

 lem is a more exact determination of the corresponding structures 

 in the unevaginated telencephalon medium of early phylogenetic 

 and ontogenetic stages. 



In Ichthyomyzon the evaginated hemisphere includes the 

 entire primary olfactory area (olfactory bulb), the greater part of 

 the secondary area and a smaller part of the corpus striatum. In 

 the telencephalon medium there is left the primordium hippo- 

 campi, a subhippocampal lobe and a part of the corpus striatum, 

 all of which are completely evaginated in higher brains, and also 

 a portion of the secondary olfactory area. The posterior part 

 of the latter is preserved in the telencephalon medium of the 

 highest brains (probably here as an olfactory center of the third 

 order) in the preoptic nucleus ('ganglion basale opticum' of 

 authors) . 



The ventricular sculpturing of the diencephalon has been 

 fully described and comparisons made with Johnston's recent 

 account. It is suggested that the homologies of these structures 

 in fishes cannot be definitely determined until fuller comparative 

 data regarding their functional connections are available. 



LITERATURE CITED 



Ahlborn, F. 1883 Untersuchungen liber das Gehirn der Petromj-zonten. Zeits. 



wiss. Zool., Bd. 39. 

 Edinger, L. 1905 Die Deutung des Vorderhirns bei Petromyzon. Anat. Anz., 



Bd. 26. 

 Herrick, C. JuDSON 1910 The morphology of the forebrain in Amphibia. Jour. 



Comp. Neur., vol. 20. 

 Johnston, J. B. 1902 The brain of Petromyzon. Jour. Comp. Neur., vol, 12. 



1910 A comment upon recent contributions on the brain of Petro- 



myzonts. Anat. Anz., Bd. 37, nos. 6, 7, 8. 



1912 ■ The telencephalon in cyclostomes. Jour. Comp. Neur., vol. 22. 

 Kappers, C. U. Ariens 1913 Localization and the significance of sulci. 



XVII Intern. Congress of Medicine, London, pp. 273-392. 

 DE Lange, S. J. 1912 The red nucleus in reptiles. Koninklijke Akad. van Wet- 



tenschappen, Amsterdam, Meeting of March 30, 1912. 

 Schilling, K. 1907 Ueber das Gehirn von Petromyzon fluviatilis. Abhand. der 



Senckenbergischen Naturf. Geselschaft, Bd. 30. 

 Sterzi, G. 1907 II sistema nervoso centrale, vol. 1, Ciclostomi. Padua. 

 Tretjakoff, D. 1909 Das Nervensystem von Ammocoetes. II. Gehirn. Arch. 



f. mikr. Anat., Bd. 74. 



