72 



STAGING OF AMPHIBIAN EMBRYOS 



it-i GILLS 



RIGHT SIDE 



GILLS 



^% 



MOU™ 



LEFT SIDE 



OPERCULAR FOLD AND TEETH - STAGE 23 



VENTRAL VIEW 



\ 



VtNTRAL VIEW 



EVE 



OPEN OPERCULUM 



y 



t 



(STAGES 23 S 23 REDUCED 33 * 

 AS COMPARED WITH SERiESi 



OPERCULUM COMPLETE - STAGE 25 



(RANA RPIENS) 



