go A GUIDE FOR THE STUDY OF ANIMALS 



Pen, a. remnant of an exoskeleton imbedded in the man- 

 tle along the dorsal side. 



Ink sac, a sac containing a dark, sticky liquid which may 

 be thrown out through the funnel into the water. The 

 opening is near the inner opening of the funnel. 



Observations. 



1. What is the shape of the squid.? To what is this 

 shape adapted ? 



2. Identify the head and the well-developed eyes. 



3. How many arms or tentacles are there.' How are 

 they arranged with reference to the mouth .' What do you 

 find on the distal ends of the arms } How do the arms 

 vary as to size .■" What does the position and arrangement 

 of the arms suggest as to their function } 



4. Identify the exhalent siphon. Where may water 

 enter the mantle cavity.' Recalling the action of the 

 siphons in the clam, suggest a method by which a squid 

 is propelled through the water. In what direction must it 

 swim .' 



5. Split the mantle along the ventral surface and spread 

 apart. Identify the long plume-like gills, the ink sac, and 

 the inner opening of the exhalent siphon. How many gills 

 do you find } 



Suggested drawings. 



a. The squid side view. 



b. The squid from the ventral side with the mantle split 

 open, arrows to show direction of water. 



1. In what ways does a squid show relationship to the 

 clam and the snail ? 



2. What has a squid gained through the reduction of its 

 exoskeleton .' What has it lost 1 What changes were 



