420 J. B. JOHNSTON 



missure but extends back in the medial wall of the hemisphere 

 beneath the hippocampus to the posterior pole, where it forms 

 the bed for the posterior pallial commissure also (Elliot Smith, 

 '03, Herrick '10). 



In the light of the whole content of the present paper it is 

 obvious that the writer would regard the supraforaminal mass in 

 question as not belonging to the paraterminal body at all but 

 to the pallium. It is without question derived from the pallium 

 of the selachian brain and is related to the lamina supraneuro- 

 porica and not to the lamina terminalis. The term paraterminal 

 body should be restricted to the basal olfactory centers in the 

 medial wall which are in relation with the lamina terminalis. 

 This body never reaches above the foramen to any significant 

 extent. The writer has recognized a small projection of the para- 

 terminal body above the foramen in selachians but it is of no im- 

 portance. Nearly the same condition exists in the mole. 



The general relations of the gray masses below the neuroporic 

 recess and the zona limitans are clear. Although we by no 

 means understand all the factors which have called forth special 

 collections of neurones in this region, we may say that they all 

 belong to the medial portion of the olfactory lobe or the medial 

 olfactory area. The tuberculum olfactorium is a basal nucleus 

 related at its two borders with the lateral and medial olfactory 

 nuclei. It consists of a deeper, more compact, layer containing 

 islands of Calleja and of a superficial layer of loosely scattered 

 cells. Both these layers are continued into the medial wall where 

 the superficial cells form a broad thin plate on the medial surface. 

 Between the tuberculum and the ventricle is the massive head 

 of the caudate nucleus and this extends around the ventral angle 

 of the ventricle to form the deep layer of the medial wall. There 

 are, therefore, superficial, middle and deep layers of cells in the 

 medial wall. The several cell aggregates have been designated 

 by various authors by such names as nucleus septi, nucleus ac- 

 cumbens septi, nucleus medianus septi, and so forth. 



The term 'septum' has been applied to two independent struc- 

 tures in the telencephalon, the^septum pellucidum of higher mam- 

 mals and the medial olfactory nucleus or area in the medial wall 



