2l8 JoLKXAL OK Co.M I'A K AT1\ K NkUKOLOGY. 



dense cells resembling Deiter's cells. There is an olfactory 

 ventricle which extends from the cerebral ventricle the 

 whole length of the cms and well out into the lobe, though 

 not to its centre. It lies in the dorsal part of the lobe and 

 retreats farther dorsad as the lobe passes into the cms. In 

 the cms itself all of the fibres lie ventrad of the ventricle 

 which is bounded laterally, as well as dorsally, merely by a 

 membrane. The entire cavity is lined with epithelium. This 

 membrane is continuous caudad with the pallium of the 

 cerebrum and, with the epithelium of the ventricle, is the 

 apparent homologue, using Prof. Wilder's terminology,- of 

 the pes, while the fibrous portion of the crus and the body of 

 the lobe constitute the pero of the olfactory. In the olfactory 

 crus the fibres are gathered into numerous bundles which are 

 separated by layers of small spherical cells. The crus, upon 

 entering the cerebrum, divides into a well-defined radix 

 mesalis and radix lateralis. 



Prosencephalon. — The mantle portion of the cerebrum is 

 represented, as usual among fishes, only by a delicate trans- 

 parent membrane, the pallium, lined with epithelium. This 

 pallium is entirely free from the basal portion of the cerebrum 

 on the dorsal and lateral aspects, and below it is free as far 

 mesad as the lateral edge of the radix lateralis of the 

 olfactory, i.e.^ the sinus rhinalis. The median fissure is not 

 prominent, being represented dorsally by a slight fold of the 

 pallium in the median line. Caudad the pallium is plicated 

 in this region to form a considerable choroid plexus. Ceph- 

 alad the median fissure is deepened until at the exit of the 

 olfactory crura a similar fold is thrust up from below and the 

 two crura are entirely separated. The pallium, however, 

 continues to envelop the crura, maintaining about the same 

 relations as in the cerebrum, i.e., attached only ventrally, 

 free at the sides and above. Thus the lateral ventricles are 

 continued cephalad into the rhinencephalon, as described 

 above. For a discussion of the cerebral ventricles see 

 beyond. 



