I 68 ZOOLOGY. 



Oral disc: zone of tentacles; intermediate zone; lip-zone; mouth; 

 siphonoglyphs (grooves in the angles of the mouth), number? 



2. Transverse Sections. 

 Body wall. 



(Esophagus; does it appear in all the sections? Siphonoglyphs? 



Mesenteries. How is the oesophagus held in position? What dif- 

 ferences do you find in the mesenteries? They are described as 

 complete (or primary), and incomplete (or secondary, tertiary, 

 etc.). 



Show by a diagram the number and arrangement of them, especially 

 of the primary. Are they in pairs? Notice the inter-mesenteric 

 chambers. Can you find the muscular thickenings in the cut mes- 

 enteries? Sketch their position. Compare with conditions figured 

 in various text-books. 



3. Longitudinal Section. 



Complete your study of the structures mentioned above. 

 Compare the complete and incomplete mesenteries. 

 Identify : 



Mesenteric filaments (on free edge of mesenteries). 

 Genital glands (developed in the substance of the mesentery near 



the edge). 



Ostia, or ring canal ; openings through the mesenteries by means 

 of which the mesenterial chambers communicate with one an- 

 other. 

 Are the tentacles solid or hollow? 



4. General Considerations. 



Make diagrams in longitudinal and transverse view to show the dis- 

 tribution and connection of the cavities of the body. Is the mouth the 

 only opening into the cavity? Describe the symmetry of the anemone. 

 Is it radial or bilateral? Give reasons for your answer. 



215. Oculina (or other branching coral). Study the branches and 

 note the position of the polyps. Is the arrangement orderly? If so, 

 describe. 



Note with a hand lens the arrangement of the septa, which grow be- 

 tween the fleshy mesenteries of the coral. Compare their arrangement 

 with that of the mesenteries of anemone. 



DESCRIPTIVE TEXT. 



216. Some authors place the sponges and the ccelenterates 

 in the same group on account of the typical barrel shape, the 

 absence of a true ccelom or body cavity, the somewhat similar 

 character and origin of the middle mass (mesenchyma), and 

 the agreement of the principal axis of the adult with that of 

 the gastrula. In the ccelenterates however there are no lateral 



