u)8 C. [udson Heirick 



amphibian and reptilian brains published in IQIO ^ The relations between 

 diencephalic and telencephalic centers there explained and the hypothe- 

 ses based upon them are clearly of the same adaptive and cenogenetic 

 nature as those here under consideration. The conclusions reached in 

 1 910 now require some revisión as to the details, but in the broad lines 

 they are supported by this inquiry into the morphogenetic factors ope- 

 rative in more primitive types of brains. 



Addendum. 



Some comments on papers deaHng with the amphibian brain which 

 have recently come to hand may be added at the time of revisión of these 

 proofs (July I 5, 1922). Gertie Soderberg - has contributed an excellent 

 account (which was greatly needed) of the histogenesis of the cerebral 

 hemispheres. Her morphok gical interpretation follows that of Holm- 

 gren, which is supported by a detailed description of the development of 

 the ceUular áreas in Rana and Tritón. Even with these additional data, 

 the evidence for the recognition of a topographically distinct área of ge- 

 neral palÜLim in Amphibia does not seem to me conclusive. 



The primordial pyriform lobe of my description (figs. 31, 32) is divi- 

 ded into two parts, a ventral nucleus olfactorius lateralis and a dorsal pyri- 

 form pallium. The first is defined as lying within the área of distribu- 

 tion of the tractus olfactorius lateralis, the second as lying dorsally of this 

 área. This interpretation presents two serious difficulties: l) The pyri- 

 form lobe in lower mammals (where the term was first applied) does lie 

 within the área of distribution of the tractus olfactorius lateralis, as Ramón 

 Cajal's detailed description demonstrates. Its cortex is directly conti- 

 nuous rostrally with the subpallial nucleus olfactorius lateralis, not dor- 

 sally of it. 2) In both Urodela and Anura fibers of the tractus olfacto- 



' This conception does not imply, as several critics have supposed, that the 

 telencephalic centers have been «derived from» the functional columns of the 

 diencephalon by migration of cells across the telencephalic boundar\^ or otherwise. 

 On the contrary, the telencephalic zones have been differentiated /;/ s/tu under 

 the functional influence of the fiber tracts relating them with the diencepalon. 



- «Contributions to the forelirain morphology in amphibians.» Acta Zoológica, 

 Ed. 3, 1922, pp. 65-121. 



