126 EMBRYOLOGY OF THE LOWER VERTEBRATES CH. 



anterior and posterior naris : tin- morphologically posterior naris 

 eoniini: t<> lie in front of that which \\as originally anterior. 



In the Amphibian and Aiimiote tin- upper tip, which compl< 

 the huccal cavity in front, is situated between the anterior and 

 posterior narial openings, so that the latter opens into the huccal cavity 



c.o 



. N'oiii.i] vi.-u- ..I ln-;il region of larva of Protopterus at stages 31 (A),' 32 (B), 34 

 i I)), 35 (E), and 36 - (F). to illustrate the devi-lopim-nt .>f tin- oliai-tm-v organ. 



'inent or^an : t.'j, external ^ill ; <//, olfactory organ ; o*/ 1 , anterior ("external ") naris; //-', 

 ) n.-uis. In C the cut \ eil line running across tin? ventral side of the head is the 

 : margin ul' the moutli: th<' darkly sh.-nled -ii)o\rs |i;issin^ imvunls ;ttid ror\\;ird> I'mni its 

 :- an- the dltact' ii'\ i ud iiii''iit s. 



^internal naris ; , \vhile tin- innm-r ivmains outside (external naris). 

 In ill.- d-\-i<,],in;j Anininti- embryo (cf. Fowl, Chap. X.) the -vneral 



arraii^'fiii'-ni -. \\liil'- ssi-niially the same as those of /'/Wf/>/f/v.s. are 

 -niin-wliat ol.scmvd l-v ill'- inod.-llin^ of the face region. The rid^e 

 which loi-ins i In- iij. pci- lip, or anterior Uumdary of the buccal oavity, 

 IB cut across l.y the olfactory *lil ; ''(-re a wide and dee] elet't. into a 



