286 THE ARCTURUS ADVENTURE 



appears, shiny and black; this increases as we go 

 farther back, and a good-sized basal plate de- 

 velops ; the raised cutting edge becomes sharp and 

 horny white and an anterior hook appears. At 

 this point, however, there is an abrupt transition 

 to the three, large, caudal plates, one in front of 

 the other and separated by about their own width, 

 each of which supports a hooked file. 



A complication, although not a negation of this 

 theory, is that in the young Xesurus, less than an 

 inch in length, the spiny ridges are said to be very 

 low and serrate, and the irregular scattering of 

 plates on the body is not discernible, develop- 

 ing only later in the life of the individual. I have 

 not seen a yellow-tail of this age, so am unable to 

 confirm or deny this statement, or to tell what 

 careful dissection of the skin might disclose. 



Much has been written about these "murderous, 

 poisonous" spines, but as far as I know, no defin- 

 ite experiments have been made as to the latter 

 quality. In the first place the defense of our 

 Xesurus is comparable rather to irregular, sharp- 

 ridged, hooked files, than to spines, so that there is 

 no possible chance of actually disabling any as- 

 sailant large enough to kill and eat them. Even 

 the force of numbers can be of little avail in any 

 initial attack, and eight hundred Xesums crowd- 

 ing about an attacking shark or barracuda could 

 do little more direct harm than hamper his move- 

 ments and partly smother him. 



I made four experiments to prove the venomous 

 quality of the mucus about the spine or any liquid 



