50 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



c. The medusa-buds (Fig. 15, y) arranged around the 

 blastostyle. Those nearest its free end are the oldest and 

 largest, and when fully developed (Fig. 15, c) they almost 

 entirely fill the cavity of the gonangium. When ready to 

 be discharged each will be seen to be a flattened medusa, 

 with a number of marginal tentacles folded down over the 

 bottom of the umbrella (Fig. 15, ^). 



d. Make a drawing of a reproductive calycle, showing 

 these points. 



II. The o^eneral structure of the medusa. Place two or 

 three stems, with ripe calycles, in a good supply of fresh 

 sea- water, and after a day or two, carefully examine it for 

 young medusa, which will be found swimming in the 

 water, usually at the surface. They are much smaller 

 than the medusa described in Section VII., and the nearly 

 flat, disc-shaped umbrella has tentacles around its entire 

 edge. In swimming the umbrella is usually carried turned 

 wrong side out, as shown in Fig. 15, E^ with the manu- 

 brium projecting from the centre of the convex surface, 

 and the tentacles turned up at their bases, so as to point 

 towards the ab-oral surface. 



a. If possible, notice the escape of a medusa from the 

 reproductive calyx. At the time of escape the tentacles 

 are folded down, as shown at 2, but within a few minutes 

 they straighten, as shown at Z), and in fifteen or twenty 

 minutes the medusa begins to swim activelv, as shown at 

 E, by vigorous flaps of its tentacles. It grows rapidly, 

 and in about an hour it appears as shown at F. 



b. Pick out one of the larger specimens with a dipping- 

 tube ; and placing it in a watch-crystal with sea-water, 

 examine it with a low power, noticing : — 



1. The manubrium (Fig. 15, D and E, k) with its 

 large terminal mouth, and stomach-cavity ; notice that the 



