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the priiiiitix e sickle told only. Williiji ivmcIi of llils portion we find 

 now also a slight ridge projecting into the venlricie, which we shall 

 liere designate by Q for briefness' sal\e. To all (hese jusi mentioned 

 prominences of the interior wall-surface corres|)ond only Aery slight 

 grooves of the exterior surface or none at all. <)idy the ridge S 

 corresponds iji future pretty accurately to a shallow gi-oove N', \vhich 

 ninst be inter])reted as the tissura hii)pocanipi. This gi-oo\e belongs 

 to that part of S which is nearest the chorioid lissui-e and fiually 

 has an almost hook-shaped beiid near the neighboui'ing lip of the 

 chorioid fissui-e. The more in the following sections .S' is arched, the 

 more also the tissura hij)pocanipi is deepened, while at the same 

 time all other ridges are levelled. Oidy the caudate nucleus remains 

 entirely ujichanged. On its surface a vvvy slight groove is temj)o- 

 rarilv seen. The gro(»\es r and t becoiue gi'adually oblileraled for 

 the greater part, s(» thai the caudate nncdeus coalesces with /"* and 

 T. The thinner part <l of the medial wall does )iol coalesce with 

 the caudate nucleus. So the bottom of the groo\ e t liiially corresponds 

 exacth' to the boi-dei- of (/ and 7. NVheu we progress still further in a 

 basal direction, the llrst coimection between the ihalamencephalon ;uid 

 the hemispheres aj)j)ears immediately Ixdow the bottom of the groove 

 r, i.e. in the former region 7' and ra|)idly increases tirst in an 

 occipito-basal direction. At the same tiiue the lauiella i/ now seems 

 to origimite in the beud Ix'twceu the caudate nu(deus and the ()[)tic 

 thalamus. 



In the following sections we liud '/ more and more c(jnjiected 

 with the lateral wall of the thalamencephalon, i.e. with the optic 

 thalamus itself. 



Tlie insertion of the lamella d seems to shift more and more 

 towards the roof of the thalamence|>halou and the lamella itself 

 seems to become shorter. It is one of the most difficult ((uestions 

 of cerebral development wiiether this shifting and shortening of 

 the lamella >/ and also the coalescence of the caudate nucleus 

 with 7' and the lateral wall of the thalanience|)halon must be 

 interpreted as a .secondary coalescence of originally separated parts. 

 Mv histological investigations of Taksus do not allow me to give 

 a detinite answer to this (pu'stion. Still uiore basal sections show^ 

 the disap[)earance of the choi-ioid tissure. Since </ has in the 

 meantime also disap[)eared, .S' passes immediately into the e|)ithelial 

 roof of the thalamencephalon oi' jirimary fore-brain. 'J'lie gi'oove-shaped 

 longitudinal de[n-ession on the surface of the corpus striatum becomes a 

 little more distinct. The tissura hippocam|)i i-es[). the tissura prima is 

 pointed so that in the cros.s-sections the well-known picture appears, 



