CAMPANTJLAEIAN HYDKOID 93 



base of support and migrate to another place? 

 Can the branches bend ? "What movements have 

 the bodies of individual zooids? Do the feeding 

 zooids have more or less mobility than the repro- 

 ductive and young zooids ? Why ? In what 

 various ways do the tentacles move ? Does the 

 ccenosarc in the branches move at all ? 



I. Feeding. — Feed a colony with very small scraps of 

 meat placed in a watch-glass of sea-water, or, 

 better, watch the capture of small animals swim- 

 ming about the colony, and compare in all re- 

 spects with Hydra. How do the tentacles be- 

 have? Are the nematocysts used in this process? 

 How is the food swallowed? Examine a liv- 

 ing zooid under the high power, and endeavor to 

 see the circulation of currents of fluid bearing 

 particles of food through the body-cavity. Can 

 you detect on the cells of the entoderm the cilia 

 whose motions cause these currents ? Do the cur- 

 rents flow through the branches and into the re- 

 productive and the young zooids ? "Why ? To 

 what does this correspond in our own bodies ? 



c. Sensation. — While watching a colony in which the 

 zooids are expanded, gently disturb the water 

 in the watch-glass. Are the zooids disturbed? 

 How do you tell? Carefully touch a single ex- 

 panded zooid with a fine bristle. What does the 

 zooid do? Are the neighboring zooids which 

 were not touched disturbed ? If so, what prop- 

 erty does this show the colony to possess ? 



General Questions. — Do you find any distinction be- 



