140 



Besides the boundary of" the mesostriatniii and hjpersdialuin in 

 some birds is marked on the ventricular side by a slight groove, 

 my /issura neo-pahieostriatica. 



In oandal direction the mesostriatnm, which extends lo the ven- 

 tricular snrt'ace becomes smaller and sniallei-, thus exhibiting a sort 

 of Cauda, which follows for some distance the caudal pole of the 

 hyporstriatum inferius, and may be called siibstuntia palaeostriatica 

 caudata (see fig. 11 and 12). 



In some large birds, like Pelicauus, the hyperstriatum and meso-striatum may 

 be separated from each oilier — starting at the ventricular side — by an obtuse object 

 without cutting, which probably is due to the medullary external lamella being so 

 richly provided with bloodvessels. 



In the centre of the mesostriatnm (or palaeostriatum augmentalura) 

 the so called basal nucleus of authors (palaeostriatum primitivum) 

 is found, a duster of large cells, separated in front of the augmented 

 part of the palaeostriatum by another lamella the lamina medullaris 

 ventralis of authors, lamina niedulliiris inlerna mihi. 



The archistriatum or nucleus amygdalae of which I shall not speak here further 

 is pushed backward and ventrally in birds by the enormous development of the 

 hyperstriatum. Consequently the fissura strio-archistriatica, so conspicuous in Lacertilia 

 and Ophidia, has become invisible in birds (as is already the case with Crocodiles). 



In order to study the embryonic development of these parts in 

 birds, I made use of haematoxyline and sil verseries of the chick 

 of 4, 5, 5^, 6, 7, 9 and 11 days of incubation and of an embryo of 

 the ostrich some days before birth. 



In a five days embryo of a chick, we find in a transverse section 

 made on the level of the foramen Monroi, four protrusions in the 

 ventricle (fig 4). The lower protrusion a is tlie eminentia basiinedialis 

 which some sections more frontally continues in the septum. This 

 forms the basi-medial grey substance and has not to do with the 

 striate complex. 



Tire other three protrusions form parts of the so called striate 

 complex. 



The protrusion b is the primordium of the palaeostriatum . Its 

 centre (less dark in fig. 4), is the ba.sal nucleus or palaeostriatum 

 primitivum, which is augmented by the surrounding darker cells, 

 . the palaeostriatum augmentatum. 



This protru.sion has only a small frontal extension (as is seen in 

 the sagittal section, represented in fig. 5. It is chiefly confined to 

 the level of the foramen Monroi and continues backward in the 

 side wall of the recessus praeopticus (r. o. fig. 5). The profusion 

 b is separated by a fissure (the /issura neo-palaeo-striatica) from the 



