It varies much in form and size, sometimes being square and sometimes round; sometimes small enough to be used as a rat-trap, and sometimes large enough to catch and hold human beings, in which case it was known by the name of man-trap. This latter form is now as illegal as the spring-gun, and though the advertisement “Man-traps and Spring-guns are set in these grounds” is still to be seen, neither one nor the other can be there. They are all constructed on the same principle, namely, a couple of toothed jaws which are driven together by a spring, when the spring is not controlled by a catch. They are evidently borrowed from actual jaws, the same words being used to signify the movable portions and notches of the trap as are employed to designate the corresponding parts in the real jaw. In both figures of the accompanying illustration we shall see how exact is the parallel. On the right hand is a common rat-trap, or gin, such as is sold for eightpence, with the jaws wide open, so as to show the teeth. On the left is a sketch of the upper and lower jaws of the Dolphin, in which an exactly analogous structure is to be seen. [Illustration: JAWS OF DOLPHIN (OPEN). RAT-TRAP (OPEN).] The figure on the right hand of the lower illustration shows a man-trap as it appears when closed, the teeth interlocking so as exactly to fit between each other. The same principle is exhibited in the jaws of the Porpoise, which are seen on the left of the illustration. The jaws of an Alligator or Crocodile would have answered the purpose quite as well, inasmuch as their teeth interlock in a similar fashion, but I thought that it would be better to give as examples the jaws of allied animals. The reason for this interlocking is evident. All these creatures feed principally on fish, and this mode of constructing the jaws enables them to secure their prey when once seized. [Illustration: JAWS OF PORPOISE (CLOSED). MAN-TRAP (CLOSED).] [Illustration: FORE-LEGS OF PHASMA. MOUSE-TRAP.] Another example of such teeth is to be found in the fore-legs of various species of Phasma and Mantis, as may be seen by reference to the illustration. The latter insects are wonderfully fierce and pugnacious, fighting with each other on the least provocation, and feeding mostly on other insects, which they secure in their deeply-toothed fore-legs. They use these legs with wonderful force and rapidity, and it is said that a pair of these insects fighting remind the observer of a duel with sabres. THE BAITED TRAP. Our space being valuable, we are not able to give many examples of Baited Traps, whether in Art or Nature.