460 C. JUDSON HERRICK 



bounded farther forward by the perfectly differentiated dorso- 

 medial cortex. A remnant of this cortex is also seen at the caudo- 

 lateral angle of the hemisphere. Similar conditions prevail ven- 

 trally of the foramen (fig. 65), save that here the precommissural 

 body occupies a much larger part of the "septum," as well as the 

 "bed" of the commissura pallii anterior. 



Laterally of the median plane the commissura pallii posterior 

 lies in contact with the stria medullaris for a short distance at the 

 rostral border of the pars dorsalis thalami and habenula (figs. 52, 

 64), and some of my preparations of Phrynosoma and Scelo- 

 porus seem to show a fibrous interchange between these tracts. 

 But my specimens of these lizards are not well adapted for the 

 study of fiber tracts and the nature of these fibers must be left 

 undecided. Most of the fibers of the stria medullaris pass far- 

 ther caudad to reach the habenula and superior commissure and 

 do not share in this contact with the commissural fibers. 



Many years ago Kupffer ('93, p. 57) commented upon the fact 

 that in the Amphibia the superior commissure lies farther rostral 

 as compared with the other elements in the diencephalic roof 

 than in most other vertebrates, and in his last work ('06) he figures 

 the relations of these elements in a large series of vertebrate 

 brains. In Amphibia the relations of the fibers of the commis- 

 sura pallii posterior have perhaps determined the position of the 

 superior commissure and in lizards we seem to have an intermedi- 

 ate condition. In all higher forms there is no direct connection 

 of any sort between the posterior poles of the hemispheres and the 

 diencephalon, probably by reason of an increase in the extent of 

 the posterior chorioidal fold and fissura chorioidea. 



Crocodilia. — The brain is more highly differentiated in the Croc- 

 odilia than in other reptiles; and T shall describe briefly some of 

 the features of the brain of a young specimen of Alligator missis- 

 sippiensis 25 cm. long, stained by the silver reduction method 

 of Cajal. 



In the mid-region of the septum (fig. 66) the nucleus lateralis 

 is seen to receive fibers from the columna fornicis and commissura 

 hippocampi as described by Cajal ('04, p. 1055) in the mouse. 

 The wide fissura arcuata extends far rostrad, as in lower mammals, 



