ASTERIAS FORBESI 181 



adambulacral ossicles, ectoneural nervous ring and ectoneural 

 radial nerve. Details should be drawn only in one arm. 



3. Examine under low power the madreporic plate and make a 

 drawing about 5 cm. in diameter showing its structure. 



4. Remove with a scalpel some of the pedicellarias, place them 

 in a drop of water on a slide, examine under microscope and 

 make a drawing showing both types of pedicellariae. 



5. (b) Injected specimen. Place the specimen in a dissecting 

 tray with water, examine the oral surface and introduce into 

 drawing No. 2 (in an arm different from the one drawn in detail 

 from the dry specimen) the ambulacral feet, eye and tentacle. 



6. Examine the aboral surface and introduce into drawing 

 No. i the branchiae. 



7. With strong scissors make a lateral incision around the 

 whole animal taking care not to ruin the internal organs. Make 

 a circular incision around the madreporic plate. Lift with a 

 forceps the dorsal body wall at the end of each arm and press 

 the digestive glands down, tearing the mesenteries with the 

 handle of a scalpel. Cut the intestine near the anus and remove 

 the entire dorsal body wall. Make a drawing of its inner sur- 

 face showing the network of ossicles and spaces between them. 



8. Make a full page drawing of the digestive system showing 

 cardiac pouches and their retractors, pyloric portion of the 

 stomach with five pyloric cceca or digestive glands, and intestine 

 with its intestinal cceca. 



9. Remove with a forceps the entire digestive system taking 

 care not to spoil the peristomial membrane. Make a drawing 

 of the reproductive organs. 



10. Remove the reproductive organs. Make a full size draw- 

 ing of the ambulacral system showing madreporic plate, hydro- 

 phoric canal, Tiedemann's bodies, the five pairs of ampullae 

 situated over the oral ossicles and belonging to the oral tentacles 

 and the four rows of ampullae in one of the arms. Show also the 

 peristomial membrane and the axial organ of the circulatory 

 system. 



