110 ECONOMIC ZOOLOGY 



the horny teeth that cover the tongue and buccal cavity, they cut 

 through the body wall and suck out the blood and soft parts until 

 the victim dies; then they seek another host. Fish are sometimes 

 found with one or more of these holes in the body wall, through which 

 a loop of the intestine may protrude. In Cayuga Lake, New York, 

 some years ago, serious damage was done the food-fishes by the large 

 lake lampreys that were abundant there, so that a systematic warfare 

 was carried on to exterminate the pests. 



The hags are parasitic in the same way upon marine fishes, except 

 that they enter the body-cavity of the host through the hole they cut, 

 and emerge again upon the death of the victim. Considerable damage 

 is thus done the fishing industry in some regions. 



Elasmobranchs. In this group are found the sharks and rays, 

 which include the largest of all the fishes. Their value as food will 

 be noted below; their negative importance will here be briefly described. 

 In this connection the so-called man-eating sharks will at once come 

 to mind. To what extent these monsters are dangerous to man is 

 difficult to determine. There were fish specialists, a few years ago, 

 who expressed great doubt as to whether man was ever attacked by any 

 species of sharks, and it is probable that the majority of sharks are 

 quite harmless, so far as attacking man is concerned. It is difficult to 

 believe, however, that all the stories that are told in the tropics about 

 man-eating sharks are fabrications, and it will be remembered that 

 during the summer of 1916 there were several apparently authentic 

 cases of loss of human life by sharks along the Atlantic coast of the 

 United States; for example; the Baltimore Sun of July 7, 1916, had these 

 headlines: "Shark Kills Bather. Bites off both Legs of Bellboy at 

 Springlake, N. J. Second Case in a Week. " 



While sharks of various species are common in the North Atlantic 

 these visits from the man-eaters were very unusual and zoologists had 

 various theories to explain the strange phenomenon. 



The shark that is usually called the "man-eater" is the Great 

 White Shark, genus Carcharodon; this monster, according to Jordan, 

 reaches a length of 25 feet; Giinther says it is sometimes 40 feet long 

 and has been known to cut the body of a man in two at one bite. It is 

 an inhabitant of tropical and subtropical seas, where it is much feared 

 in some regions, by the water-loving natives. The other sharks, though 

 they may reach a large size, are probably, as has been said, quite harm- 



