164 Deferred Papers. [June 16, 



found in all other Mammals concern the rhinencephalon, the hippo- 

 campus, and the cerebral commissures. 



The olfactory bulb is quite free from the frontal portion of the 

 hemisphere. Its stalk is exceedingly thin, and connected with the 

 under surface of the hemisphere near the median line. The portion 

 of the mantle which receives it is separated from the general surface 

 by a deep incision (ectorhinal fissure), which extends in depth almost 

 to the mesial surface. The pyriform lobe thus formed merges with 

 the general surface far back on the mesial aspect of the hemisphere, 

 at the spot at which the hippocampal fold commences. 



The hippocampus is very extensive; it lies entirely dorsal to the 

 velum infcerpositum, and is continued forwards to the extreme 

 anterior end of the brain. With the rhinencephalon it forms there- 

 fore a loop, open in front. 



No commissural fibres cross the incisura pallii longitudinalis 

 dorsally to the hippocampus. For reasons stated in his paper, the 

 writer considers that fibres which cross from one hemisphere to the 

 other on the peduncular (portal) side of the fascia dentata cannot be 

 homologous with the corpus callosum, and he therefore concludes that 

 this structure is completely absent from the brain of Ornithorhynchus. 

 A strong commissure or decussation lies within the concavity of the 

 rhinencephalic loop, but its fibres are restricted in their distribution 

 to the hippocampal fold, as shown in sections stained after Weigert's 

 method. The convex portions of the mantle are entirely dependent 

 upon the anterior commissure for mutual connexion. 



Exception being made to the incisura rhinalis and dentary fossa as 

 not belonging to the category of fissures, the cortex is completely 

 destitute of convolution. 



Each hemisphere of the brain was cut into a series of sections, the 

 anatomical features of which were described in detail. 



XVII. "Contribution to the History of the Interchange of 

 Pulmonary Gases in the Respiration of Man." By WILLIAM 

 MARCET, M.D., F.R.S. Received June 9, 1892. 



[Publication deferred.] 



XVIII. "Magnetic Properties of Pure Iron.' 1 By FRANCIS 

 LYDALL and ALFRED W. S. POCKLINGTON. Communicated 

 by J. HOPKINSON, F.R.S. Received May 4, 1892. 



[Publication deferred.] 



