76 



TiLXKY AM) U'THKK F. YVAKKKX 



however, thai the structure can be found in human embryos, though 

 in a rudimentary and inconstant condition. 



'I'he so-called post velar lultules or divert icula can lie clearly fol- 

 lowed in every decree of complexity in embryos of 1!) nun. up to 44 

 nun. and appeal' in every specimen studied in those statics. They 





40 33 32 



i !_' Mesial view of forebraiii reconstruction of 70 mm. cut cmliryo. X 2.">. 

 Tlie unshaded ;irc;i shows the cut surface of the reconstruction. According to 

 Tilney. I'.ll.V 



_'. cliiasmat ic process; (. chiasm ; .">. corpus interpedunculare ; 7. epiphysis; !, 

 fora ii ii MI of Moiiro : l.'i. infinidiliular process; '_' 1. midl>niin : L'7, iiiiiiiiiuillary liody; 



:!'_'. post-chiasmatic eininence: :;:;. post-chiasmatic recess; 34, post -infundibular 



eminence; '!"'. po>l-infuinlil)iilar recess: :;.s, pre-chiasmatic recess: 10. recess of 

 infundibular process; 41. supra-optic crest; !_'. supra-optic recess. 



Iteii'in at the dieiicephalic lip of the \-eliim, have definite limits ;md 

 involve ;i relutively short extent of the oi-;d end of the dieiicephalic 

 roof-|)lale. They always appear as out u'rowt hs from the lirain roof 

 and are to lie distinguished from ingrowths due to plexus formation. 



Vs'isi-rcn's 117 deseriplioii of the coiidit ions in ihc sheep is as 

 follows: 



