54 



PS. A 



lamina terminalis (s) forming a bilaminar (in Marsupials) hippocampal 

 commissure (Fig. 2 ps. d., ps. v.) ^). From each of these parts of the 



fornix fibres proceed forwards in the "sep- 

 tum" and precommissural area to constitute 

 the Riechbündel (Fig. 2 R). Other fibres 

 enter the anterior (dorsal) part of the fornix 

 and run backwards to all parts of the hippo- 

 campus. These fibres arise in the cells of 

 the precommissural area, tuberculum olfac- 

 torium, olfactory peduncle and bulb (bundle 

 of fascia dentata). 



In placental Mammals the anterior (dor- 

 sal) part of the hippocampus and the dor- 



f>S.v 



Fiq. 2, 



QEJS. 



F)g. 2. Semischematic representation of the commissures in Fi;?. 1. ^ 5. 

 af columnae fornicis ; B Riechbündel lying in precommissural area {p a). 



sal limb of the fornix commissure (ps. d.) disappear; the corpus 

 callosum making its appearance in the place occupied by the latter, 

 the induseum griseum representing the former. A number of fibres 

 which proceed to the posterior (ventral) part of the hippocampus 

 in the "dorsal fornix" of Marsupials, maintain in Eutheria their 

 ancestral course and proceed to their destination (Fig. 3) above 

 the corpus callosum as the striae mediales Lancisi. Others run obli- 

 quely backwards and upwards in the septum as the fornix longus 



stTio. "ledi'alis Lane 





I© «/ 



^^3. 



d-ZS. 





• r 



Fig. 3. Scheme of same region in a placental Mammal. 



l) Preliminary Communication on the Cerebral Commissures. Proc. 

 Linn. Soo. N. S. W., Vol. IX, Pt. 4. 



