141 



tiiberciilum c wliirh is less protruding but continues further front- 

 ally tliaii f), bending down more or less to the base of the brain. 



Fig. 4. Transverse section of the forebrain of a chickembryo of 5 days 

 on the level of the foramen Monroi. b = primordium of the 

 palaeostriatum. c — primordium of the hyperstriatum inferius, 

 d = primordium of the hyperstriatum superius. For a see text. 



This protrusion c appears to be tiie pvimoidiuni oi' \he /it/per-'iriatmn 

 inferius. Candalij the groove which separates it from 6 fades away, 

 the cells of t' extending over b (^comp. also fig. 6). 



Dorsally from c, arising equally from the mantle is d, merely a 

 thickening of the pallium in this stage wliicii however appears to 

 give rise to the hyperstriatum superius. 



Figure 6, representing a sagittal section, is taken from an 

 embryo of six days of incubation. The section siiows the lelation 

 of the hyperstri'ituin inferius c to the palaeostriatum augmenlaium 

 b, which extends frontally to tlie triangular fissure, a part of the 

 fissura neo-palaeostriatica. 



It is further seen that c, the hyperstriatum inferius, arises on 

 this level from the basal region in front of the palaeostriatum cor- 

 responding with the tuberculum olfactorium (t. o.). The hyperstriatum 

 inferius thus partly has a basal origin ^partly because more laterally 

 it is continuous also with the mantle as we already saw in the 

 transverse section of fig. 4). 



10* 



