Stage Number 



23 



Age. in Hours at IS** Centigrade 



216 



24240 



Length in Millimeters 







OPERCULAR rOLD 



TE.E.TM 



OPERCULUM CLOSED ON RIGHT 



25 



284 



OPERCULUM COMPLETE. 



(From "Stages in the Normal Development of Rana pipiens," by Waldo Shum- 

 way. Reprinted from Anat. Rec, 78, No. 2, October 1940.) 



29 



