GONIONEMUS 1 



1. Examine with the naked eye, in a watch glass containing water, a 

 preserved jellyfish of the hydrozoan type, such as Gonionemus. Note 

 the gelatinous consistency of the body and the umbrella, or dome, shape. 

 The upper convex surface is called the aboral, or ex-umbrella, and the 

 lower concave surface is called the oral, or sub-umbrella. 



2. Study the oral surface of the specimen with a dissecting microscope. 

 Note : (a) the tentacles attached near the periphery, each with an adhe- 

 sive pad near its tip ; (b) the perforated, circular diaphragm (velum) at- 

 tached below the tentacles; (c) the central structure (manubrium) sus- 

 pended inside from the center of the ' umbrella ' and made up of (d) the 

 wide-lipped mouth, which opens into (e) the enteric cavity. 



3. Radiating from the base of the manubrium are (e) the four radial 

 canals bearing (/) the reproductive glands (gonads). The radial canals 

 lead to the periphery of the disc where they connect with (g) the circular 

 canal, which encircles the periphery near where the tentacles are attached. 

 Note also (h) the sense organs which are located about the margin of the 

 body at the base of each tentacle and also between the bases of some of the 

 tentacles. 



4. Make (a) a drawing of the specimen from the oral surface and (6) a 

 drawing from the side, to show the structures observed. 



5. For comparison, examine representatives of the other classes of 

 Coelenterates, such, for example, as the common large Jellyfish (Aurelia), 

 the Sea Anemone (Metridium), and a calcareous Coral. (W. fs. 39-42.) 



i B. pp. 68-73. 



273 



