146 EMBRYOLOGY OF THE LOWER VERTEBRATKS en. 



case with Protuj'tcri's, the luiccal roof in front, that is to say in the 

 neighbourhood of the mesial plant', passes without interruption into 

 the external skin: in other words the maxillary ridge is not con- 

 tinued to the mesial plain- BO as i<> m< , i its fellow. In later stages 



ar 



end. 



N 



E 



FIG. 80. Sagittal sections through Polypi. 



A,stage]4; H, sta-c 17 ; C, stage 20 ; I), stajje 2S; E, stage 24 +. ct, anu ; or , archenteroj 

 endoderm; *nt, enteric cavity ; /./-. cavity ,,f fnn-liniiri : /.;/, fm.-ut ; N, notochord ; t ,.f, |.rim:ir\ Inl.l 

 nr liraiii I1<x>r; pin, pineal ru.lirn.-nt ; .v.c, cavity of .sj.inal r..r,| ; //. yolk. 



thereof of the mouth would be hidden in ,i view fnun the ventral 

 side owing to the forward growth of the lower jaw. 



The anterior portion of the huecal cavity in l'i-<,,l,-le Aiiij.hiliians 

 arises in a iinnm-i- essentially similar in that deserihed above. 



In the Gjmnophiona and the Amninta a e.haraeter^tie modiliea- 

 tion nf the mouth margin is hroiio-ht aii.mt l.\ tin; tact thai, as 



