1 64 ELEMENTARY ]UOLOGV. [CHA1\ 



r;. The branchial pore ; asymmetrical and situated 

 on the left side (external branchiae are no longer 

 present). Remove the ventral portion of the 

 adjacent integument (coalesced opercula) ; a 

 spacious brajichial chamber Avill be exposed. 

 Note its limits. 



0. The i/itcrnal brancJi'uc ; paired vascular folds of 

 the sides of the head, four sets on cacli side, 

 lying within the branchial chamber. 'i>y and 

 make out their relations. They arc l)orne uj)on 

 outgrowths of the wall of the pharynx {branchial 

 visceral arches), which alternate with perfora- 

 tions of the same {I'isceral clefts) putting tlie 

 l)haryngeal cavity in communication with the 

 branchial chamber. 



t. The lungs; seen, on opening up the body- 

 cavity, as small diverticula of the alimentary 

 canal not yet distended with air. 



0. The larva on the appearance of hind-limbs. 



Examine from beneath. 



a. The body generally ; note the proportions of its 

 several constituents. 



/?. The vioutJi; its large size ; papillate lips and 

 horny teeth well marked. 



y. The absence of suckers and branchial pores. 



8. The hind-limbs ; small, but fully differentiated ; 

 one-third the length of the body and separated 

 in the ventral middle line by the terminal por- 

 tion of the alimentary canal. 



<. The fore limbs ; differentiated, but covered by 

 (visible through) the opercular membrane. 



