I.] THE FROG. 163 



Examine from the side. 



e. The mouth; surrounded by a protractile bell- 

 shaped suctorial lip, and utilized for purposes of 

 adhesion, in place of the suckers which are now 

 disappearing. 



Cf. the movements of the living larva. 

 m. The development of the operculum. Look for larvae 

 intermediate between k and /. Examine from the 

 side. 



The operculum will be seen arising, on either 

 side, immediately in front of the external gills, as a 

 backwardly-directed fold of the second (hyoid) 

 visceral arch. 



n. The larva at a later stage than I ; conspicuous by 

 the great length of its tail and the absence of 

 external branchiae. Examine from beneath, 

 a. The body generally ; clad in a thin transparent 

 integument, elegantly pigmented in black and 

 gold. 



ft. The mouth; still increasing in size, the cir- 

 cum-oral papillae becoming more marked. 



7. The suckers ; still further reduced and repre- 

 sented by two small vestiges. 



S. The intestine; visible through the body-wall as 

 a greyish coiled tube of large calibre. 



e. The anus (cloacal orifice)-, median and ventral, 

 situated at the base of the tail on the summit of 

 the pointed posterior extremity of the trunk 

 (cf. side view). 



The hind-limbs ; minute papillate outgrowths of 

 the body- wall, at the sides and a little in front of e. 



II 2 



