226 H. F. Osborn 



lamina termiualis of Ran a. He figured them very accurately and 

 compared the uppermost, from its relations, to the corpus callosum: 

 »Da es die Lobi cerebrales unter einander verbindet, lässt es sich 

 wohl als Andeutung eines Corpus callosum ansehen.« To the lower 

 bundle he did not give any further designation. 



Stieda (1S70 pag. 36 and 46) confirmed Reissner's observation 

 but regarded the two bundles in the Frog's brain as both belonging 

 to the anterior commissure and, as far as I know, was the first to 

 suggest the homology which has since been generally adopted : «Ich 

 fasse das obere Bündel nicht als Corpus callosum, weil die Lagerung 

 desselben am Boden der gemeinschaftlichen vorderen Hirnhöhle mir 

 zur sonstigen Lage des Corpus callosum nicht recht passen will. 

 Mir vielmehr scheint es, als ob beide Querbtindel der Commissura 

 anterior der Säuger nach Lage und Aussehen sehr bequem zu ver- 

 gleichen sind; das untere Bündel würde dann dem in die Corpora 

 striata, das obere Bündel dem nach vorn in die Tubercula olfactoria 

 hineinziehenden Theil entsprechen.« I may call attention to the fact 

 that this interpretation was founded upon an observation of the course 

 of the upper bundle fibres regarding which the author himself spoke 

 very doubtfully (pag. 37). This fact has been overlooked by sub- 

 sequent writers (cf. Mihalkovics 1875). 



Goette's hypothesis (1875) that the union of the olfactory lobes 

 in the Batrachia represents the first step towards the septum in which 

 the corpus callosum appears, was shown by GtEGenbaur (1874) to be 

 entirely untenable. 



Bellonci's (1882 and 1883 pag. 194) observations upon Ran a ac- 

 company his interesting papers upon the commissural and other relations 

 between the olfactory lobes and the hemispheres. (1) There is a 

 lower internal olfactory tract which extends backwards and forms 

 an incomplete chiasma (this is not figured). (2) From the upper 

 part of the olfactory region, where the olfactory lobes pass insen- 

 sibly into the hemispheres, a tract of delicate fibres takes origin and 

 extends backwards, with its concavity inwards, joining the median 

 plane above the anterior commissure of which it forms the superior 

 bundle, «chiasma olfactoriae« (pars olfactoia). This tract is in part 

 a true commissure, in part an intercrossing of fibres, from which 

 chiasma fibres issue in the direction of the anterior optic ganglion. »Toute 

 fois c'est un entrecroisement de fibrilles plutot qu'un veritable com- 

 missure« (1882 Taf. II Fig. 6). (3) The lower bundle of the anterior 

 commissure extends transversely and is truly commissural. There 



