57 



nolfl 



the cerebellum, as seen from the surface, are not well shown by 

 Fritsch, but, in general, his figure is richer in detail than mine, it 

 shows all the cranial nerves, and on the whole, is very excellently 

 executed. His figure shows also the stump of the new nerve, a circum- 

 stance which will be referred to later. 



But, the point of chief interest now is the new nerve. Its gan- 

 glion is large and readily seen from above; it is situated at the base 

 of the median division of the bulbus. In large specimens of Galeus 

 canis, the brain is coated with a covering of gelatinous consistence, 

 with a number of connective tissue strands and blood vessels running 

 through it. In removing this covering the nerve will also usually be 

 removed. The ganglion varies in form and size in dilferent specimens. 

 In one specimen (not the one drawn) it was deeply pigmented and, 

 therefore, very obvious before any dissection had been made. 



In the specimen drawn there were three branches of the nerve 

 in front of the ganglion. The largest one, as shown in the figure, 

 passes forward and later- 

 ally over the base of the 

 bulbus, and into the fis- 

 sure separating the two 

 divisions of the olfactory 

 nerve. The other two 

 branches are slender and 

 join the median division 

 of the fila olfactoria. 



In Scoliodon ter- 

 ras novse. — In this shark 

 (Fig. 21) the separation of 

 the great divisions of the 

 olfastory nerve is very 

 marked. The division ex- 

 tends through the bulbus 

 and even the tractus is 

 bifurcated behind the 

 bulbus. The brain is of 

 the compact type, the 



cerebellum overlying the mesencephalon and coming into contact with 

 the thalamencephalon. 



The new nerve is connected to the ventral surface of the pros- 

 encephalon, in the median plane about midway between the optic 

 chiasma and the anterior tip of the prosencephalon. In some speci- 



Fig. 21. Dorsal view of the brain of Scoliodon 

 terrse-novse, nat. size. 



