LOLIGO PEALII. 125 



mens in aquaria should be studied. Do you know what they 

 eat and how they capture their food ? 



Study a small living specimen in a jar of sea- water and no- 

 tice: 



1. Its general shape and distinct head. 



2. Its position in the water. For convenience, the lower 

 surface may be referred to as ventral, but this is not to be con- 

 sidered as morphologically the same as the ventral surface of 

 other Mollusca. What parts are kept moving? Why is water 

 pumped when the animal is not swimming? 



3. In what direction it can swim best. Can it swim in the 

 other direction? How does it swim? Is the funnel movable? 

 How does it guide its movements? 



4. Its color. Irritate it and see what happens. What pur- 

 pose does the change in color serve? What is the ink for? 



5. What happens when the end of a finger is placed within 

 the circlet of tentacles of an animal about two inches long that 

 is being held firmly? 



Using an adult specimen, observe: 



6. The arrangement of the arms on the head. Are they ar- 

 ranged in any definite order? Are they all alike? 



7. The suckers of the arms. Do they follow the same order 

 on all of the arms? 



8. The structure of a sucker. Notice the peduncle, outer 

 thin margin, horny ring, and piston. Is the horny ring smooth? 

 What is its function? How does the sucker work? Split one 

 and draw the cut surface. 



9. The mouth. Where is it placed? Notice the tips of the 

 horny beak. Which jaw is longest? 



10. The eyes. 



11. The fold of tissue behind each eye. These have been 

 called the olfactory organs. 



12. The attachment of the head and the extent of the mantle 

 opening around the neck. 



13. The funnel protruding from beneath the mantle on the ven- 

 tral surface. Notice the position and character of its opening. 



