430 EMBRYOLOGY OF THE LOWER VERTEBRATES oh. 



t'iG. 197. — Stages in the development of Polypterus. (All except A after drawings 



by Budgett. ) 



A, stage 12 ; B, 28 ; C, 27 ; D, 31 ; B, 33 ; F, 36 ; G, larva 30 mm. in length, a, anus ; o.o, cement 

 organ ; E, eye ; e.g, external gill ; op, operculum ; p.f, pectoral tin ; y, yolk. (A-E x 11 ; F x 8.) 



