20 STUDIES OF ANIMAL LIFE. 



a. Is the bud in every respect like the parent Hydra ? 



b. What becomes of the bud ? (Watch it from day 

 to day.) 



c. Draw a budding Hydra. 



2. Occasionally a Hydra may be seen with little bunches 

 projecting from the surface of the body containing 

 either egg or sperm cells. Those containing the egg 

 cells are the more distal and are called ovaries, while 

 those containing sperm cells are called spermaries. 



I. Suggestive Questions. 



1. In what direction must " contractile fibers " extend 



to enable the Hydra to shorten itself so quickly ? 



2. How must they be arranged to lengthen the Hydra's 



body? 



3. Does the Hydra need any special organ for breathing? 



4. In what different ways does tlie Hydra show " division 



of labor " ? 



5. In what important particulars is the hydra-plan of 



structure like the grantia-plan ? 



6. How does the Hydra differ essentially from the 



Grantia ? 



J. Extra Work. 



1. Examine a thin cross-section of the body wall and draw 

 ectoderm and endoderm cells and also nettle cells. 



2. A CAMPANULARIAN HYDROID. 



Note : Since practically all hydroids and hydro-raedusse are marine in 

 their habitat and since living material can only be obtained near the sea- 

 shore, these studies are based entirely on preserved specimens. 



A. The Hydroid Colony. 



1. Examine the entire hydroid colony with reference to 

 its general appearance, and fragments of a colony 



