Stage Numbeir 



d 



9 



Age. in Hours at Id" Centigrade 



96 



16 



Length in Millimeters 



4 



MUSCULAR RESPONSE. 



ME. ART BEAT 



20 



140 



6 



GILL CIRCULATION 



MATCHING 



162 



1 



MOUTH OPEN 



CORNEA TRANSPARENT 



22 



192 



5 



TAIL FIN CIRCULATION 



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

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



28 



