1 64 ELEMENTARY BIOLOGY. [CHAP. 



7]. ThQ branchial pore {spiracle) ; asymmetrical and 

 on the left side (external branchiae are no longer 

 present). Remove the ventral portion of the 

 adjacent integument (coalesced opercula) ; a 

 spacious branchial chaviher will be exposed. 

 Note its limits. 



B. The internal branchice ; paired vascular folds of 

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

 lying within the branchial chamber. Try and 

 make out their relations. They are borne upon 

 outgrowths of the wall of the pharynx {branchial\ 

 visceral arches), which alternate with perfora- 

 tions of the same {visceral clefts) putting the; 

 pharyngeal cavity in communication with the 

 branchial chamber. 



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

 cavity, as small diverticula of the alimentaryj 

 canal not yet distended with au-. 



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



Examine from beneath. 



a. The body generally ; note the proportions of its 



several constituents. 

 /?. The 7nouth; its large size; papillate lips am 



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 per- ^ 

 tion of the alimentary canal. 



€. lL\iQ. fore limbs; differentiated, but covered byj 

 (visible through) the opercular membrane. 



