42 CCELENTERATA. 



Make a drawing of the animal. 



2. Drop a few grains of sand on the tentacles. Observe and 

 record what happens. Repeat, placing the sand on the oral 

 lips, the siphonoglyph, and the oral disk successively. Try the 

 same using sawdust soaked in clam juice. Repeat, using clam 



meat. 



What conclusions can you make: first, as to the ability to 

 distinguish food; second, as to methods of obtaining food; and 

 third, in regard to ciliary action? 



3. Stimulate the animal with a needle at various points 

 and try to determine where it is most sensitive. Observe its 

 manner of contraction. When fully contracted, if the irritation 

 is continued, thread-like structures, acontia, are thrust out 

 through minute pores, cincUdes, in the body- wall. 



Make a drawing of the contracted animal. 



Internal Anatomy. — Using preserved material, place the edge 

 of a razor across the peristomial area, at right angles to the 

 mouth-slit, and divide the animal from disk to base into 

 halves. 



1. Note the extent of the esophagus and siphonoglyphes; 



they lead into the ccelenteric chamber. Find the extent of this 

 chamber, and the method of its subdivision by delicate parti- 

 tions, the mesenteries, or septa. Are all of the mesenteries 

 alike? 



2. Forming the free edges of the mesenteries, below the 

 esophagus, are the convoluted mesenteric filaments, which are 

 secretory organs that are probably equivalent to the gastric 

 filaments of the Scyphozoa. 



3. Quite near the bases of the mesenteries are the attach- 

 ments of the acontia. What relation have they to the mesen- 

 teric filaments? Mount living acontia under a cover-slip in 

 sea-water and notice the central muscle strand, nematocysts, 

 and cilia. 



4. Also located on the mesenteries, and arranged parallel 

 to the filaments, but back from the edge a bit, are the repro- 

 ductive organs or gonads. Are they found on all of the mesen- 



