416 C. JUDSON HEBPICK 



eminentia septalis, ganglion basale, format io pallii lateralis and 

 eminentia pallii medialis. The two ventral parts are Gaupp's 

 pars inferior s. subpallialis hemisphaerii and the dorsal parts are 

 his pars pallialis (Gaupp, '99, fig. 29, p. 107). The dorsal and 

 ventral parts are sometimes separated by well marked total 

 fissures or by a conspicuous difference in internal structure. The 

 fissure which separates the two lateral parts is the sulcus limitans 

 lateralis of Gaupp and is incompletely homologous with the fissura 

 endo-rhinalis (Turner) of other classes of vertebrates. The two 

 medial parts of the frog are also separated by a total fissure, the 

 fissura septo-corticalis of Kappers. Gaupp names this fissure 

 the sulcus intermedins on the ventricular side and fissura arcuata 

 on the superficial side. For reasons which will appear in the sub- 

 sequent discussion, I name it fissura limitans hippocampi. The 

 positions of both fissures in the frog are marked internally by a 

 characteristic disposition of cells and fibers termed the zona lim- 

 itans (lateralis et medialis), and the zona limitans may be present- 

 as a useful landmark in cases where the corresponding fissure is 

 not externally evident. 



URODELA 



Ainbly stoma 



We will first examine a series of transverse sections through 

 the brain of a specimen of larval Amblystoma 17 mm. long and 

 about 35 days of age after fertilization. The relations are very 

 similar to those of the larvae of Necturus described b} T Warren 

 ('05, 18 mm. stage) and by Kupffer ('06, 24 mm. stage) though 

 with a less pronounced flexure in the thalamus region. 



At the level of the olfactory bulb (fig. 1) the wall of the hemis- 

 phere is massive on all sides and the five parts as defined above 

 are not separate. Secondary olfactory fibers (tractus olfactorius) 

 are present around almost the whole periphery. The olfactory 

 bulb is limited to the lateral aspect of the hemisphere. 



A short distance caudal to the bulb (fig. 2) the greater part 

 of the medial wall becomes membranous. This septum ependy- 

 male separates the dorso-medial from the ventro-medial part of 



