Ti^KNKK, Mo)-f>I/o/ooy of tJic Avian Ih-aiii. 63 



towards the rhinencephalon. When there is only one olfac- 

 tory lobe this projection terminates in the olfactory cms. 

 When two olfactory lobes are present, an extension of this 

 projection enters each olfactory lobe and expanding, forms 

 the olfactory ventricle. 



PROVENCE PHALOX. 



Tf'w/r/c/f' (Plate V, Figs. 3,3,6,7; Plate VI, Figs. 3-5, 8, 10; 

 Plate VII, Figs. 1-5, 7). — For convenience the ventricle may 

 be divided into the following parts: 



1. A narrow cavity, which is approximately parallel to 

 the meson. 



2. A lateral expansion of this cavity. This expansion 

 curves over the dorsal portion of the axial lobe. 



3. A common expansion of both of the above cavities. 

 This expansion curves around the caudad portion of the axial 

 lobe, and then turning, passes cephalad as far as the 

 crura cerebri. 



Thus a large portion of the caudad part of the axial lobe 

 of each hemisphere is surrounded on all sides, excepting the 

 cephalic and lateral, by the ventricle; while a small portion 

 of the dorsal part of the axial lobe of each hemisphere is sur- 

 rounded on all sides, excepting the ventral, by the ventricle. 



The first part of this ventricle is, approximately, a triangle, 

 with its base near the dorsal surface and its apex near the 

 ventral surface of the prosencephalon. This cavity lies near 

 the meson, but is not parallel to it. Near the dorsal surface 

 of the prosencephalon it is diverted laterad by a local thick- 

 ening of the cephalad portion of the mesal wall o^ 

 the ventricle. At the same level, but near the caudad 

 extremity of the prosencephalon, a local swelling of the 

 dorsal portion of the mesal wall of the ventricle causes 

 a laterad displacement of the ventricle. Slightly caudad 

 to this place a small convex portion of the axial lobe pro- 

 jects into the ventricle. The two above-mentioned swellings 

 of the mesal wall of the ventricle are connected by a narrow 



