26 STUDIES OF ANIMAL TYPES 



is expanded at the ends of the branches into cuplike forms 

 in which the nutritive zooids sit. Are all the nutritive 

 zooids expanded ? They can contract and withdraw into 

 the cuplike ends of the branches, and, no doubt, some will 

 be foungi in those positions. Note the immature zooids 

 at the ends of some of the branches. 



Look along the hydrorhiza, near the base of the hydro- 

 caulus, and in the axils of the side branches, for smooth, 

 club-shaped bodies. Note that they resemble a large cap- 

 sule and contain many globular bodies. These are the 

 reproductive zooids. They contain the medusae buds. After 

 a time the capsule (gonotheca) breaks open, and the me- 

 dusa buds escape, and develop into umbrella-shaped 

 medusae, or, as they are often called, jellyfish. After 

 swimming about for a time the medusae produce eggs that 

 in turn develop into the plantlike structure which we are 

 now studying. 



Make a drawing showing all the points mentioned. 



IX. THE STARFISH 



Materials. Specimens of starfish preserved in formalin or 

 alcohol, also some living specimens, if possible, dissecting instru- 

 ments, fine-pointed syringe, carmine, brittle stars and sea urchins 

 for comparison. 



Directions. (Those living inland can obtain starfish from 

 a dealer in supplies of that kind. See page 110. Such specimens 

 will be preserved in alcohol or formalin.) 



A. EXTERNAL FEATURES. Note the color of the body 

 above. In one common species the bluish ones are the 

 females while the lighter colored ones are the males. Note 

 that the body and rays are more or less flexible, yet hard. 



