BR.l 



BR.2 



MT 



B 



FIG. 2oA. Side view of a tadpole at the time of hatching, x 16. 

 B. Ventral view of the same tadpole. 



BR.I, external gill of first branchial arch; BR.2, external gill of 

 second branchial arch ; OS, stomatodaeal pit ; MT, mesoblastic somites 

 seen through the skin ; OC, olfactory pit ; Q, cement-organ or sucker ; 

 u, proctodaeal or cloacal aperture. 



To face p. 100. 



