AURELIA, METRIDIUM 59 



Study a somewhat older ephyra and find the starting of 

 the adradial canals and the beginning of the formation of 

 adradial cushions. Examine a series of older stages and find 

 how the adradial cushions expand, how the canals branch, 

 and how the circular canal is formed. 



Make drawings of the stages. 



By way of comparison, examine demonstrations of Cyanea, 

 Dactylometra, Lucernaria, or other forms belonging to this 

 group. 



Hargitt: Variations among Scyphomedusae. Jour. Exp. ZooL, 11, 1905. 



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

 medusae. Jour. Morph., 21, 1910. 



Mayer: Rhythmical Pulsation in Scyphomedusae. Carnegie Inst, of 

 Washington, 1906. 



ACTINOZOA 



METRIDIUM (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. 



Specimens for laboratory study should be placed in 

 aquaria, and left undisturbed until they are fully expanded. 

 In experimenting be very careful not to overstimulate. 



1. Notice the shape and attachment of expanded, living 

 specimens 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. 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. 



