NERVUS TERMINALIS IN AMIA 



61 



There is a definite membrane about the nasal capsule except 

 where the olfactory nerve originates and for a slight distance 

 anterior and ventral therefrom. 



At a period three hours later, or about nineteen hours before 

 hatching, a slight increase has taken place in the number of large 

 cells in the placode near the origin of the olfactory fibers. The 

 latter are not numerous, being confined to three or four sections 



Fig. 2 Transverse section of a embryo Amia 22 hours before hatching. Shows 

 contact of the paired olfactory placode with the neural tube. Preparation as 

 above. X 450. 



six micra thick. Some cells which have the characters of neuro- 

 blasts are now seen within the brain wall near the point where 

 the brain has raised slightly to meet the olfactory nerve. This 

 is the beginning of the olfactory bulbs. There are mitoses in the 

 layer of germinative cells next the brain ventricle. Also, mitotic 

 figures are seen here and there throughout the nasal placodes 

 which have no lumen as yet. A slightly greater space exists at 



