462 



PEOr. G. ELLIOT SMITH OX THE MORPHOLOGY OF THE 



corpora paraterminalia. The typical relationship existing between the thalamus and 

 the corpus striatum in this section calls for no description. 



ne. 



A coronal section through the brain of SpJunodon passing iuimediately Ijehind the lamina terminalis 



(Dendv's foetal stage E). 



If another coronal section be made midway between the upper extremity of the lamina 

 terminalis and the commissura aherrans, the epithelial roof of the cmla Avill be found to 

 present a very differetst appearance to the simple fold which was shown in the last 

 figure. 



Upon each side an elongated and irregular fold of the epithelial roof is bulged through 

 the foramen of Monro (or porta, as Wilder haj^pily calls it) into the lateral ventricle, 

 where it forms the lateral choroid plexus, as the accompanying figure 9 shows. A 

 comparison of this illustration with the preceding one at once shows that this choroid 



Fig. 9. 



Portion of a coronal section through the brain of S/Aenodou (Dend.y"s stage E), midway between the upper 

 extremity of the lamina terminalis and the cuiiimissura aherrans. 



plexus is not a portion of the wall of the hemisphere which has retained its embryonic 

 character, but a part of the roof of the neural tulje, which, as His has 2)ointed out, never 

 becomes anything else than neuroglia or simple epithelium. 



The careful study of the disposition of the lateral chorioid plexus in almost any Vertebrate, 

 or better in a series of Vertebrates, proves beyond a doubt that the choroid plexus 



