The origin of the Corpus callosum, a contrib. upon the cerebral comiu. etc. 533 



In studying the brain of Eniys (loc. cit. p. 242) I found that 

 a portion of the callosal bundle, ca/', corresponds in position with 

 the crura fornicis, but as no columnae, or descending fibres, were 

 observed and the entire bundle see- 

 med to pass into the opposite he- 

 misphere I compared it to the 

 commissura cornu ammonis. 

 In T r p i d n 1 u s however such 

 descending fibres are readily ob- 

 served and I am strongly inclined 

 to believe that they are homo- 

 logous with the mammalian fornix. 

 My present series of sections do 

 not clearly demonstrate the course 

 of this tract into the hippocampal region, therefore a positive solution 

 of this interesting question must be deferred until a better series of 

 sections can be prepared. 



/y— 



Transverse section of the brain of Emys euro- 

 paea, throng the cerebral commissures. 



Aves. 



If the brain of a duck, Anas boschas, be carefully removed 

 from the skull and the membranes uniting the hemispheres cut, 

 these bodies may be gently separated until the anterior commissure 



Fig. Ü. 



Sagittal section of the brain »fAnas boschas. 



comes into view ; immediately above and behind this is a fine white 

 strand of fibres', quite as figured by MbCKEL (1816:, and so distinct 



• A. BuMM, Das Großhirn der Vögel. Zeitschr. f. wiss. Zool. Bd. 3S, 18S3, 

 pag. 4.30 — 467, mentions this commissure but accepting Eabl-RCckiiard's au- 

 thority does not recognize its homology with the corpus callosum. 



