290 THE ARCTURUS ADVENTURE 



rose into place, like the nuchal fringe of any ambly- 

 rhynchus, and as the annoying fish did not swerve 

 aside, the dainty yellow and black Chaetodon went 

 through a hundred graceful threatenings, rearing, 

 ducking, dipping far to one side, and making swift 

 passes at his opponent, bringing the whole body 

 into play. Now and then it would jerk upward 

 with all its force, with an unexpectedness which 

 the other fish could only just manage to avoid, — 

 and which, if it struck home, would work real 

 damage. 



In the triggerfish, the anterior dorsal spines 

 have become quite as specialized a means of defense 

 as the spine of the surgeon. Complete detachment 

 has been brought about from the functional part 

 of the back fin, the first spine being long, often 

 serrated, and usually held in place by a second 

 smaller one (Fig. 46). 



Leaving the family relations and the devious 

 and obscure ways by which the yellow-tails have 

 won and are holding their present enviable posi- 

 tion, let us consider the details of their fitness for 

 the everyday labor of life. Our name of cows 

 was given because of their everlasting grazing, 

 nibbling, nibbling, nibbling, at the plant and 

 animal fodder which covers the rocks. The habit 

 of going in such enormous schools, and crowding 

 closely together made them a spectacular feature 

 of every island where I dived, and their manoeuv- 

 ers were astounding. Several hundred approached 

 swimming slowly along, when, as if at a signal, 

 all would stop, and if over a rather flat bottom. 



