34 CCELENTERATA. 



outer extremity are calcareous concretions or lithites, and a pig- 

 ment-spot or ocellus. Each tentaculocyst is protected aborally 

 by a hood-like projection, and on the sides by marginal lappets. 



(6) Two depressions, one above and the other below the 

 tentaculocyst. These have been assigned olfactory functions, 

 and are called the olfactory pits. 



Make a drawing showing the profile of the entire animal, and 

 show the structure of at least one quadrant, as seen from the oral 

 surface. 



If time permits study a developmental stage, "ephyra," and 

 compare it with the adult. 



By way of comparison, examine demonstrations of Cyanea, 

 Dactylometra, Lucernaria, or other forms belonging to this group. 



Hargitt: Variations among Scyphomedusse. Jour. Exp. Zool., 11, 1905. 



Hargitt, C. W. and G. T. : Studies in the Development of Scyphomedusse. 

 Jour. Morph., 21, 1910. 



Mayer: Rhythmical Pulsation hi Scyphomedusae. Carnegie Inst. of Wash- 

 ington, 1906. 



ACTINOZOA; 



METR1DIUM. (Sea-Anemone.) 



Specimens are quite common on piles, as well as on rocky 

 bottoms, and may be easily observed by means of a glass- 

 bottomed pail. Most of the observations can be made much 

 better on specimens in aquaria, but it is desirable to see their 

 natural surroundings. 



1. Notice the shape and attachment of expanded, living speci- 

 mens in an aquarium, or in a deep finger-bowl. The free end, 

 called the disk or peristome, is fringed with tentacles, and the 

 elongated mouth is located in the middle of this area. At one 

 or both angles of the mouth the lips are thickened into what is 

 called a siphonoglyph. 



Make a drawing of the animal. 



2. Feed a specimen with bits of mashed clam to ascertain 

 its manner of taking in food. Drop bits on the tentacles at one 

 time, and disk at another. 



