Johnston, TJie BTain of Petromyzon. 41 



the epistriatum, constituting about half of the fibers which 

 end there. 



The cells of ihe caudal part of the striatum proper (Figs. 

 18, 19) are placed near the cavity and arranged in rows as are 

 the cells of the epistriatum. The cell bodies are stellate or fusi- 

 form and some have central processes which run to the central 

 cavity. The fibers from the epistriatum are the only ones which 

 I have found ending in the striatum. The neurites pass backward 

 from the striatum to end in the thalamus. I have not found 

 these neurites going to any other region than the central grey 

 of the thalamus (and mid brain ?). They do not enter the hy- 

 pothalamus. This renders it probable that the striatum fibers 

 are distributed to the thalamus alone in Acipenser, where it 

 was impossible to determine this point owing to the union of 

 fibers from the striatum and olfactory area in one tract. 



b. Area olfactoria. 



This includes the whole caudal portion of the lateral ex- 

 pansions of the fore brain (Figs, i, 18, 30). The wall is of 

 about equal thickness throughout and consists of a central mass 

 of cells and fibers with only a thin peripheral fiber zone free 

 from cells. The cells are numerous, are stellate or bipolar and 

 have long dendrites spreading widely through the whole wall. 

 The whole area is penetrated by fibers from the olfactory lobe, 

 many of which are traced with perfect ease in all my preparations. 

 Most of the cells send their neurites upward and backward into 

 the dorso-caudal part of the area where they collect into a large 

 tract at the junction of the olfactory area with the epistriatum 

 and thalamus. Here the tract bends around the sharp angle 

 made by the junction of these parts and runs caudo-dorsad 

 through the epistriatum into the ganglia habenulae, where it 

 ends as described above (Figs. 16, 17, 18). This is the largest 

 part of the tractus olfacto-habenularis. 



The remainder of the neurites run from the ventral wall of 

 the olfactory area through the striatum into the hypothalamus 

 as the tractus olfacto-lobaris described above (Figs 18, 30). 



c. Nucleus thaeniae. 



The olfactory area is closely related over the outer surface 



