330 JouKNAi, OF Comparative Nei'roi.ogy. 



The buffalo fish ( Cai-piodcs) furnishes an illustration of 

 long-stalked olfactories. The crura are enormously elongate 

 and the ventricles extend a long distance upon the dorsal 

 surface of the crura proper, being covered by a thin pallium 

 similar to that of the hemispheres. 



The arrangement is well seen in Fig. i , Plate XIX, where 

 the dorsal pallium has been removed from the cerebrum but 

 remains on the crura. The sections (Figs. 4-5, Plate XXI) 

 illustrate substantially the same arrangement as seen in the 

 black-horse ( Cycleptus). The radix lateralis is wider than 

 its fellow and very thin vertically, while the radix mesalis is 

 rather compact and enters the ventro-mesal angle of the 

 cerebral hemispheres. 



The radix lateralis first becomes attached to the cerebrum 

 by its lateral border. Then the mesal radix becomes attached 

 to the mesaxial lobe, which is here quite distinct, thus cut- 

 ting off" a spur of the ventricle, which remains distinct some 

 distance caudad. The connection with the common ventricle 

 or aula is upon the cephalic aspect, affording evidence that 

 the porta? in this case may almost be said to lie entirely 

 cephalad of the hemispheres. The forward extension of the 

 ventricles beyond the cerebrum is, we believe, a fact of 

 primary importance in imderstanding the morphological 

 significance of fish brains. The subsequent course of the two 

 radices are distinct, and corresponds to that described in the 

 black-horse {Cycleptus) , which furnishes one of the best 

 illustrations of the tubular olfactory crus. Transverse sec- 

 tions show that the arrangement of ventricles, etc., is the 

 same as that described by my brother in the cat-fish. The 

 transection of the crus cephalad of the cerebrum shows it to 

 be composed of a tubular sheath of membrane, with the fibres 

 collected in two somewhat distinct bundles along the ventral 

 surface, entering the radix lateralis and mesalis respectively. 

 There is, however, a narrow band of fibres between the 

 sheath and the epithelium lining the ventricle. The ven- 

 tricle passes into that of the cerebrum at a point where the 



