LOLIGO PEALEII. 137 



CEPHALOPODA. 

 LOLIGO PEALEII. (The Squid.) 



Specimens of this or closely related species are rather common 

 along the Atlantic coast of the United States. They are active 

 swimmers, but may occasionally be seen in shallow, quiet water 

 near the shore. The movements and positions of adult speci- 

 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. 



