206 SCIENCE REMAKING THE WORLD 



it is dislodged it invariably returns to its singular 

 lodging place. The fish is brightly coloured, being of 

 a brilliant vermilion hue with three broad white cross- 

 bands. The discoverer of this pe- 

 culiar habit suggests that there 

 are mutual benefits to fish and 

 polyp from this habit. The fish, 

 being conspicuous, is liable to at- 

 tacks, which it escapes by a rapid 

 retreat into the sea anemone; its 

 enemies in hot pursuit blunder 

 against the outspread tentacles of 

 the anemone and are at once nar- 

 cotized by the "thread cells" shot 

 out in innumerable 

 showers from the ten- 

 tacles, and afterward 

 drawn into the stom- 

 ach of the anemone 

 and digested. 



There are more 

 than one thousand 

 species of insects, in- 

 cluding various cock- 

 roaches, beetles, flies, 

 etc., that live in 

 ants' nests in various kinds and degrees of symbiotic 

 association with their ant hosts. In some cases this 

 symbiosis takes on a very highly specialized form. 

 For example Wheeler (the foremost student of ants and 

 an entirely reliable observer) has worked out the follow 



Underground nest of the 

 bumblebee 



