A CAMPANULARIAN HYDROID 25 



Note that some individuals have small hydras attached 

 to the sides of their bodies. Hydras reproduce by budding 

 (see text, page 49). 



D. TOPICS FOR FURTHER STUDY. Give the leading 

 characteristics of the hydra. Discuss its manner of obtain- 

 ing and digesting food, its reproduction, and movement. 

 Compare it with a sea anemone, coral polyp, and jellyfish. 

 Fix firmly hi mind the position of the hydra and its rela- 

 tives in the animal kingdom. 



VIII. A CAMPANULARIAN HYDROID 



Materials. Campanularian hydroid, glass slides, cover glasses, 

 compound microscope. 



Directions. (This ccelenterate lives in the sea attached to 

 rocks, seaweed, etc., and may be obtained from any of the dealers 

 mentioned on page 110.) 



Mount some of it in water on a glass slide. Note with 

 the naked eye its resemblance to a plant. What color is it ? 

 What is the general form of the animal? The stem with 

 its branches is called the hydrocaulus. Note the horizon- 

 tal, threadlike stems running along the surface of the sea- 

 weed to which the animal is attached. Note that the hy- 

 drocaulus is attached to these stems, which are called the 

 hydrorhiza. What surrounds all the stems and branches? 

 This transparent sheath is called the perisarc. Inside the 

 perisarc note the dark rod, or axis. This is the ccenosarc. 

 Note that it runs into all the branches and connects with 

 the zooids. 



It will be noted that there are two kinds of zooids, the 

 nutritive and the reproductive. The nutritive are situated 

 at the ends of the side branches. Note that the perisarc 



