fish aided by the thresher-shark. The fierce gladiator was said to attack from below, goading his mighty adversary to the surface with his terrible weapon, while the thresher, at the top of the water, belabored him with his long, 
Fig. 2.—Sword of Young Sword-Fish. lithe tail. Skeptical modern science is not satisfied with this interpretation of any combat at sea seen at a distance. It recognizes the improbability of aggressive partnership between two creatures so different as the sword-fish and a shark, and explains the turbulent encounters occasionally seen at sea by ascribing them to the attacks of the killer-whale upon larger species of the same order.
Such a large animal as the sword-fish can have but few formidable antagonists. The tunny, or horse-mackerel, other sword-fishes, and sharks, are its only peers in size, and of these the sharks are probably its worst foes. Mr. John A. Thomson, of New Bedford, states that the bill-fish is an inveterate enemy. Bill-fish appear about the last of the season, and the sword-fish are sure to leave soon after. Many species of parasites are found upon the sword-fish; some hang on the gills, others fasten themselves to different parts of the alimentary canal, and others still bore into the flesh. They may be divided into two groups, worm-like parasites and crustacean parasites, the latter resembling small crabs and lobsters. Several species, as might be expected from the size of the fish, are among the giants of their races. There is also a species of remora or sucker which is often found attached to the gill-cover of the sword-fish, and to no other fish. It is, however, to be regarded as a messmate rather than as a true parasite.
