54 ^- MITSUKUKI ; 



" Anlage," although divided into two shows a distinct 

 henii-chonia on each side. 



e is nine sections behind d. The neurenteric canal is just 

 closing. The mesoblast is not distinctly separated from 

 the wall 0Î the neurenteric canal but is specially continu- 

 ous with the chorda -\yavt of the neurenteric wall. 



f is next behind e. The neurenteric canal is now clearly 

 closed below. The mesoblast is fused with the wall of the 

 canal alono; its whole heisfht. 



g is four sections behind/. The dorsal median part of the 

 section which has been more and more vaulting from 

 a backwards is now clearly recognisable as the beginning 

 of the tail-swelling. The continuation of the neurenteric 

 canal is open above (this opening begins in the section 

 next in front) and tlie epiblast is reflected downwards at 

 the edge of the opening to hecome continuous with the mass 

 below. The wall of the neurenteric canal, although clearly 

 recognisable as such by the arrangement of their cells, is 

 amalgamated with the rest of the "Endwulst" mass, 



h is four sections behind g. It is behind the posterior wall 

 of the neurenteric canal and shows the last vestiges of its 

 wall. There is a median dorsal groove — the primitive 

 groove — continued backwards from the dorsal opening 

 of the neurenteric canal (f/). At its lips, the epiblast 

 is reflected downwards and becomes continuous with the 

 mass below. 



i is three sections behind //. The tail-swelling is more and 

 more distinctl}^ recognisable as such, rising as a nearly 

 separate body above the general surf ice of the blastoderm. 

 The mass Avithin — the "Endwulst" — is compact and 

 homogeneous ; it is united dorsally at the lips of the 

 primitive groove with the epiblast on each side, and ven- 

 trally by a rather broad stalk with the mass below. I^ote 

 that the lateral plates of the mesoblast are below and do 

 not take part in the formation of the tail-swelling. 



