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Show 134 REV. S. J. WHITMEE ON THE HABITS OF FISHES. [Feb. 5, spines, viz. protection against the attacks of those of the class which are carnivorous. I have never seen a fish try to use its dorsal spines actively to strike with. But I have seen a Batistes swim rapidly past an antagonist, and graze its side with its file-like lateral spines. I a m strongly inclined to believe the dorsal and anal spines are used for defence only. There is little doubt that most carnivorous fish capture their prey by outswimming them, as most carnivorous quadrupeds capture theirs by outrunning them. In the shallow waters within our reefs it is a very common thing to see shoals of fish leaping out of the water when chased by the larger ones which prey upon them. They pass along with a series of springs at a great rate; and the noise they make is heard at a long distance. Most fishes thus chased would, if captured, be seized from behind. If so, the strong spines on the anal and dorsal fins, inclined as they are backwards, would often be of immense value to their possessors in preventing them from being swallowed. I a m inclined to believe this is the chief, if not the sole, use of these spines1. If this view be correct, those fish most exposed to the attacks of others which are carnivorous ought (other things being equal) to be best protected. I have not given sufficient attention to the subject to say whether this be so or not. But from a merely superficial examination I fancy further investigation would prove that spiny fishes are more frequently found in confined and shallow waters, where they have little opportunity of escape ; and that slow-swimming fishes are most frequently protected with peculiar defensive armature. The Diodon and Tetrodon may serve as examples of the latter. They swim slowly, and if unprotected would be specially liable to be preyed upon by carnivorous fish. Unless alarmed neither look formidable. In both of them the spines are ordinarily concealed in the soft and loose skin ; and then they present a very different appearance from the stuffed specimens or plates by which they are chiefly known. But the individuals of both genera possess the power of very rapidly inflating their loose skins, and thus erecting the spines with which they are more or less completely covered. In the case of the Diodon there can be no doubt that its inflated and bristling appearance would serve to protect it from attack; and I imagine the most voracious monster would think twice before attempting to feast on the less-protected Tetrodon. 1 Since the above was written I have seen a proof of the correctness of this view as to tbe use of spines. I was one day passing along the lagoon on the shores of Upolu, when m y boatmen noticed a great splashing in the water at a distance Knowing the cause, they pulled for the place. There we saw a large fish with a smaller one sticking in its jaws, caught apparently by the erected spines. They got separated just as we approached, and before m y crew could secure them ; but the natives told m e they not unfrequently take fishes in that way. Sometimes they find both dead, one firmly sticking by its spines in the jaws of the other.-December 1877. |