102 



THE BIOLOGY OF THE AinMAL 



drawings of several specimens to show the normal shape 

 and abnormal variations. 



i. Size. — What is the size of an ordinary specimen? 

 Can you tell anything about the age by the 



size? 



c. Color. — What is the natural color? Are aU the 



living specimens colored alike ? Is the color the 

 same aU over the body? Are there any color 

 markings on the body? What changes of color 

 take place when the specimen is dried ? 



d. Structure. — The central part of the body is called 



1. The disk. — What is its shape? How does its 



oral dififer from its aboral side? 



On one side of the disk find a circular 

 plate, 



2. The madreporic body — Position ? Shape ? 



Size ? Color ? Structure ? 



The two rays which touch the madreporic 

 body form 



3. The bivium. — What differences between these 



rays? 

 The remaining three rays form 



4. The trivium. — Compare with 3. 



The ray opposite the madreporic body is 

 called 



5. The anterior ray. — Compare in shape, size, 



and structure with the other rays. 



6. The spines (in studying these a dried speci- 



men should be used for comparison). — On what 

 part of the body are they found ? Are there 

 any traces of definite arrangement ? How 

 many kinds are there ? What is their shape ? 



