44 



FREDERICK TILXEV A XI) LUTHER F. WARREX 



tune before the appearance of the paraphysis. In the embryo 

 of an 11 nun. Miixtclus the evagination appears rising well 

 above the general plane of the roof. 



It is bounded by a thin cephalic and a thicker cauda 1 wall. 

 A recess of considerable depth extends into it; it retains com- 



29 



Fiu. 11 Mesial vie\\- of forebrain reconstruction of 11 nun. Mustelus embryo. 

 X 100. The unshaded area shows the cut surfaces of the reconstruction. Ac- 

 cording to Tilney. 1!H.">. 



1, cliiiism : 7. epiphysis; IN, infundibular evagination; 21. midbrain; 2.~>, mam- 

 in ill a ry region : _"., optic e vaginal ion; 36, post-in fund! I )iilar (-vaginal ion ; -H, tel- 

 encephalon; L5, tuberculum postero-superius; 46, tubercle of the Boor of Schulte 



inimical ion \vilh tin- third ventricle. The inception of the velum 

 transversum may be discerned, but no paraphysis is pi'esent. 

 r l'he changes observed in passing from the 1 1 mm. to the 'JO mm. 

 embryo consist in the now definite ap|>"arance of the velum 

 transversum and the elongation of the pineal organ. 



