Literary Notices. xxi 



duncles, which in bony fishes have somewhat different connections 

 than those here described. 



The mesencephalon resembles that of amphibia. Two ventral ex- 

 pansions in front of the region of the oculomotor may be thought to 

 give plausibility to the theory that the mesencephalon is composed of 

 three neuromeres. That one of these corresponds to the hypoaria 

 does not seem to have occured to Dr. Burckhardt, who identifies these 

 bodies with a protrusion of the diencephalon cephalad of the hypophy- 

 sis. The oculomotor arises from two niduli. Aside from these roots 

 the mesencephalic roots of the trigeminus and the optic tracts arise in 

 the mesencephalon and there pass into it fibres from the supracom- 

 missure, and postcommissure; the lemniscus and Meynert's bundle 

 and the dorsal longitudinal fasciculus, basal prosencephalic tract and 

 cephalic cerebellar peduncles pass through it. 



The diencephalon is almost exictly as in amphibia. The form 

 of the roof is very simple and gives a good idea of its typical structure 

 in all vertebrates. Great divergence in nomenclature has existed 

 which arose out of misinterpretation of the various elevations and 

 modifications of the roof. Burckhardt applies the term conarium to 

 the homologue of the dorsal sac of fishes. This is in communication 

 with the praeplexus cephalad and the velum caudad. The latter is 

 continued backward in the socalled pineal pillow (Zirbelpolster). The 

 pineal proper lies behind the supracommissure So far from these 

 relations being abnormal, they may be recognized in all vertebrates. 



It seems to the the writer that Dr. Burckhardt is in error in iden- 

 tifying the ventral protrusion of the diencephalon ( tuber cinereum ) 

 with the hypoaria (lobi infeiiores. ) 



The hypophysis is a' most exactly as in amphibia. Burckhardt 

 distinguishes lobi hippocampi upon the caudo-lateral aspects of the 

 hemispheres as the writer has done in bony fishes and demonstrates a 

 connection with the olfactory lobes. The latter are divided into 

 tuber, tract and bulb. A large protuberance on the ventral surface 

 beneath the tubers forms a lobus postolfactorius. The presence of a 

 rudimentary cortical layer is of interest as probably indicating the 

 first appearance of the cortex among vertebrates. The precommis- 

 sure is well developed but the so-called " mantle bundle" of Edmger 

 is absent. The callosum is present in the form described by Osborn. 



Wiedersheim had described in 1876, in Phyllodactylus europceus, 

 a sac with many branching diverticula, filled with otolith-sand and 

 lying in relation to the choroid plexus of the 4th ventrical. Hasse 

 had previously seen in Amphibia a similar structure, which Coggi had 



