THE NOTOOHORD. 



in. 



Fig. 34. A SERIES OF TRANSVERSE SECTIONS THROUGH THE NEURENTERIC AND NOTOCHORDAL CANAL 



OF A MOLE EMBRYO. (Heape.) 



The embryo was slightly more advanced than the one represented in Fig. 25. The dorsal opening 

 is shown in I., continued into the primitive groove ; the canal passes thence through the column of 

 cells which unites, the epiblast and hypoblast at the front of the primitive streak (II. ), into the noto- 

 chordal thickening of the hypoblast (III.), along which it extends for some distance (IV.), and 

 eventually opens ventrally (V. ) into a median groove, which is formed in the notochorda! thickening 

 (n.ch.c. ) 



ep, me, hy, epiblast, mesoblast, hypoblast ; p.gr. (in I. and II.), primitive groove ; c, neurenteric 

 or notochordal canal ; m.gr. (in III., IV., and V.), medullary groove. 



VOL. I. D 



