STARFISH 103 



Size ? structure ? Are they fixed or movable ? 

 If the latter, what kind of joint have they? 

 Do you find any spines which seem to be spe- 

 cially adapted to certain purposes? Notice 

 the five clusters of spines around the mouth, 

 forming the mouth-papillae. 

 Draw one of each kind of spine seen lengthwise. 



7. The skin. — Does it cover all parts of the body? 



Examine its texture. What is its color? Do 

 you find any variations in thickness ? Is it 

 loosely or closely attached to the hard parts of 

 the body ? "With fine forceps remove a small 

 piece of skin from the body of a living starfish 

 and examine in a drop of sea-water with the 

 high power. Note the columnar ciliated 

 epithelium.. 

 Among the bases of the spines find 



8. The aboral tentacles. — How are they ar- 



ranged on the body ? How do they compare 

 in shape, size, and structure with the ambula- 

 cral feet ? Is their surface ciliated ? 



9. The mouth. — What is its position ? Shape ? 



Size ? Are there any teeth ? Lips ? 



Around the mouth - opening find a mem- 

 brane, 



10. The peristome. — Shape ? Structure ? Color ? 



Is it flexible ? Does it bear any structures ? 

 On the oral side of the rays look for 



11. The ambulacral grooves.— What is their po- 



sition on the ray? Shape? How are they 

 formed ? What is their relation to the mouth ? 

 How far do they extend ? Where is the deep- 

 est part of the groove? Where the shallow- 

 est? 



