THE PHILOSOPHY OF XESURUS 285 



The great numbers of these fish show that they 

 are successful wagers of life, and their conspicu- 

 ous pattern and coloring combined with their 

 absolute fearlessness indicate that they have some 

 adequate defense against the creatures on every 

 side, who would gladly devour them. The mouth 

 is absurdly small, with wholly inadequate teeth, 

 as far as biting is concerned, so as to that method 

 of defense these submarine cows are on a par with 

 the grazers of the land. They have no long, strong 

 tail to lash, nor have they the static defense of the 

 funny little box-fish, and their flesh is not at all 

 poisonous, but delicious eating, as we proved more 

 than once. So we must fall back upon the caudal 

 armature as the crux of the matter. 



The surgeon or doctor fish show a beautifully 

 graded series, from a form which has a long, curved 

 lancet, sharp as a surgeon's scalpel, folded forward 

 into a groove on the side of the tail, to others, at the 

 opposite end of the scale, which have only a sha- 

 green-like roughness of the skin. Xesurus lies not 

 far from the lower end of this series, meaning, by 

 lower, the more primitive condition. It seems 

 probable that this whole group is descended from 

 some form which had, as a defense, the entire body 

 covered with bony plates, from the center of each 

 of which arose a curved spine. In Xesurus these 

 have degenerated until there is left only an irreg- 

 ular group of ten to fifty small, black, dermal 

 plates, scattered over the posterior third of the 

 body. The most anterior are mere spots of dark 

 pigment, then a minute, central, rounded nodule 



