115 



poc. olf. 

 no If. I. 

 Tns'ence. 



cup has been removed. The new nerve, as in former cases, has a gan- 

 glion connected to the brain by two roots. It crosses the fore-brain, 

 passes in front of the median division of the olfactory, behind two 

 slender bundles of the lateral division, and finally conies into connec- 

 tion with the large outer bundle of the lateral division. On the left 

 side the principal blood-vessels {va. sgn.) are indicated. In the other 

 sketches they have been omitted. 



The brain of an embryo 47 mm long as seen from above is re- 

 presented in Fig. 29. On the right side, the surface of the olfactory 

 cup and the various 

 bundles of the olfactory -n.nov. 



nerve have been ex- 

 posed by a dissection, 

 while on the left, the 

 tissue covering these 

 parts has not been re- 

 moved. The new nerve 

 (n. nov.) is seen on 

 both sides, and on the 

 right side its connec- 

 tion with the lateral 

 division of the olfactory 

 is represented. This 

 lateral division (n. olf. I.) 

 has been broken free 

 from the olfactory lobe 

 in order to show better 

 the point of union. The 

 nerve connects with the 

 brain by two slender 

 rootsand has a ganglion 

 near their place of at- 

 tachment to the brain. 



In Fig. 30 is shown the brain of an embryo 68 mm long viewed 

 from above. A shallow furrow now divides the fore-brain into right 

 and left portions. As in the specimens already described, there are 

 two slender roots and a proximal ganglion not far from their union 

 with the brain. A dissection of the chief bundles of the olfactory 

 nerve has been made on the right side, to show the course of the 

 new nerve, and its point of union with the outer bundle of the lateral 

 division of the olfactory. Near the two great divisions of the olfac- 



Fig. 29. Brain of embryo of Squalus acanthias 47 mm 

 long. X about 2. 



