AMPHIOXUS LANCEOLATUS. 207 



5. Make thick free-hand sections of various regions and 

 study with a low power in a watch-glass, to supplement the 

 study of stained sections. 



6. Prepared sections should be studied that show the follow- 

 ing five regions: (a) buccal cavity; (h) anterior part of pharynx; 

 (c) posterior part of pharynx with gonads and liver; (d) atrio- 

 pore; (e) anus. 



The five sections should be studied w4th a low powTr and 

 drawn. In (6) (anterior part of pharynx), note especially the 

 limits of the coelom and atrium, the lymph-spaces in the meta- 

 pleural folds, the two dorsal aortce, the ventral aorta, the epibran- 

 chial groove, the endostyle, the suh-endostylar coelom, and the two 

 kinds of gill-bars, primary and tongue-bars. 



With a high power study the nerve cord (best shown in re- 

 gion a) and the gill-bars and endostyle (best shown in region b), 



Draivings of these regions are desirable. 



Willey: Amphioxus and the Ancestrj^ of Vertebrates. Columbia Univ. 

 Press. 



