CELL MASSES IN THE FOREBRAIN 431 
simpler selachian brains. This tended to produce a caudal 
pole pushing back over the stem or ‘prethalamic’ portion. To 
understand the formation of the caudal pole it is essential to see 
that the expansion began in this dorsal region and proceeded 
in the direction eventually assumed by the choroid fissure and 
the hippocampus. From such a beginning the stretching of the 
hippocampus and pyriform lobe and the migration of the olfac- 
tory area over the striatum all are readily understood. The 
further expansion of the pallium and the differentiation of special 
centers in it must be the subject of future work for which the 
present is preparatory. 
LITERATURE CITED 
CasaL, S. Ramén 1904 Textura del sistema nervioso del hombre y de los 
vertebrados. Tomo 2. 
Epincer 1904 Vorlesungen, 7th edition, vol. 1; 1908, vol. 2. 
JoHNsTON, J. B. 1910c¢ The evolution of the cerebral cortex. Anat. Record, 
vol. 4. 
1911 a The telencephalon of selachians. Jour. Comp. Neur., vol. 21. 
1913 b The morphology of the septum, hippocampus, and pallial 
commissures in reptiles and mammals. Jour. Comp. Neur., vol. 23. 
Kaprers, C. U. Artens 1908 Weitere Mitteilungen iiber die Phylogenese des 
Corpus striatum und des Thalamus. Anat. Anz., Bd. 33. 
pE Langs, 8. J. 1911 Das Vorderhirn des Reptilien. Folia Neuro-Biologica, 
Bd. 5. 
