Now, I wish especially to call the reader’s attention to the curiously exact parallel between the water-boatman and the human oarsman. As the reader may probably know, the oar is a lever of the second order, _i.e._ the power comes first, then the weight, and then the fulcrum. The arm of the rower furnishes the power, the boat is the weight to be moved, and the water is the fulcrum against which the lever acts. I have more than once heard objections to this definition, the objectors saying that the water was a yielding substance, and therefore could not be the fulcrum. This objection, however, was easily refuted by taking a boat up a narrow creek, and rowing with the oar-blades resting on the shore, and not in the water. [Illustration: OAR-LEG OF WATER-BOATMAN.] [Illustration: OAR OF BOAT.] [Illustration: WATER-BOATMAN ROWING ITSELF.] [Illustration: OARSMAN ROWING.] Now, the swimming legs of the water-boatman are exact analogues of the oars of a human rower. The internal muscles at the juncture of the leg with the body supply the place of the rower’s arms, the leg itself takes the office of the oar, and the body of the insect is the weight to be moved, and the water supplies the fulcrum. Even the broad blade at the end of the oar is anticipated by the fringe of bristles at the end of the leg, and its sharpened edge by the shape of the insect’s limb. Besides these resemblances, there is another which is worthy of notice. All rowers know that one of their first lessons is to “feather” their oars, _i.e._ to turn the blade edgewise as soon as it leaves the water. Nothing looks more awkward than for a boatman to row without feathering. (We all must remember the eulogy on the “Jolly Young Waterman,” who “feathered his oars with skill and dexterity.”) In the first place, he must lift his oar very high out of the water, and, in the second, he will be impeded by any wind that happens to come against the blades. The Water-boatman, however, does not lift its legs out of the water after every stroke, as a human boatman does, and therefore it has no need to feather in the same way. But there is even greater need for a feathering of some kind in the insect’s leg, on account of the greater resistance offered by water than by air, and this feathering is effected by the arrangement of the blade-bristles, which spread themselves against the water as the stroke is made, and collapse afterwards, so as to give as little resistance as possible when the stroke is completed. * * * * *