138 



(hypopallial, Ell. Smith ^) growth, extending far backward, where 

 it is continuous with the piriforna and ammoncortex, this archistii- 

 atum keeps its contact with the olfactory area in front of the 

 Foramen Monroi, near the primary "Anlage" of the epistriatnm 

 (nncl. tr. olfact. lateralis in Reptilia: Crosby'). 



One might be inclined to ask, how it is possible to ascribe this hypopallial 

 growth to neurobiotaxis — as Ell. Smith does — if the majority of aferent 

 fibres (tr. cortico epistriaticus) comes from the periphery 



Such fibres indeed cannot account for this mode ot growth. But the archi- 

 striata (sec. epistr.) of both sides are connected by a very strong commissure, 

 which thus provides them with medial impulsus and moreover it receives aferent 

 fibres from the basimedial grey by the taenia terminalis fibres. Both systems must 

 be made responsible for the medial intraventricular growth of the archistriatum. 



Whilst this arcliistriatura which is thus derived from the innerside 

 of tiie mantle (Injpopallium Ell Smith ') forms the larger part of 

 the intraventricular mass in Chelonia (where the paleaostriatum is 

 but smalli a new striate substance which is only very small in 

 turtles, becomes evident in Lacerlilia, Ophidia and Crocodiiia: the 

 veostriatwn. Moreover the paleaostriatum, the original basal nucleus 

 of the forebrain, enlarges considerably in these animals {palaeo- 

 striatum augmentatum or mesostriatinn). 



Whereas the /xilaeostriatnrn augmentatum is really an increase 

 from tiie same matrix from which the paiaeostriatum primitivum 

 arises, and from its immediate surrounding (corresponding approximati- 

 vely with the tuberculum parol fac tori um) the neostriatum is an 

 entirely new addition starting in Reptilia as I pointed out in 1908^). 

 It arises from two sources. i°. from the base of the brain in front 

 of the paiaeostriatum and 2° from the lalero-frontal mantle joining 

 this region, as has been pointed out by Ell. Smith (1. c). The 

 paiaeostriatum, but chiefly the neostriatum receives its stimuli from 

 the tweenbrain and this may be the neurobiotactic cause of its 

 intraventricular medio-caudally directed growth. 



The neostriatum together with the archistriatum (which is separated from it in 

 Ophidia and Lacertilia by a deep fissure, tlie flss. strio archistriatica), is called 

 htjpopalUum by Ell. Smith, on account of their character as an ingrowth of 

 the pallium. 



1) Vida infra. 



') The forebrain of Alligator raissisippensis, Journ. of Gomp. Neur. Vol. 27, 1917. 



') A preliminary note upon the morphology of tlie corpus striatum. Journ. of 

 Anat. (English), Vol. Llll, 1919. 



*) Die Phylogenese des Rliinencephalons, des Corpus Striatum und der Vorderhirn- 

 commissuren. Folia Neurobiologica Bnd. I, 1908. 



Weitere Mitteilung zur Phylogenese des Voiderhirnes und des Thalamus, Anat. 

 Anzeiger Bnd. 1908. 



