266 



THE RISE OF ANIMAL LIFE 



Fig. 12-17. Members of the class Cephalopoda are conspicuous by their many tentacles or arms and their lorge 

 complex eyes. The squid (Loligo) is a common member of the class. This one is resting on the bottom of an 

 aquarium. Note the siphon just below the eye which controls the squid's direction of movement. Also note the 

 contracted chromatophores which cause the animal to appear light in color. 



mer, it is often pursued by large fish and 

 by some whales. When it is hard pressed 

 by its enemy, it can resort to another 

 method of defense. Near the base of the 

 siphon is a sac filled with inky fluid which 

 can be discharged into the excurrent si- 



phon, thus spreading a cloud of murky water 

 which obscures the vision of the enemy and 

 hides the squid. Here again this animal has 

 employed a defensive device which man 

 has only recently used in warfare. Other 

 interesting adaptations of deep sea squids 



fonword 



-^- backward 



Fig. 12-18. Locomotion in the squid. In order to go forward the siphon is directed backwards; to go backward the 



siphon is swung around so that it directs the water forward. 



