Why does the leech advance faster than other worms ?

Because the organs of adhesion are double, one at each extremity, the mouth adhering to one part of the surface, while the tail is brought up towards it, and is fixed, the body being at this time like an arch. The head then quits its hold, the body extends itself, and, and when at full length the head is then attached, and the tail brought up. By these alternate movements, the leech, at every step, advances nearly the length of its own body. - Fleming.

The stomach occupies the greatest part of the body in the leech, and is divided internally, by means of ten imperfect fleshy partitions, into somewhat separate portions.

Why is the wound of the leech of three-sided form ?

Because within its mouth are three semicircular projected bodies, with a sharp toothed edge, with which it bites.

Why is a certain species called the flying leech ?

Because it has the power of springing, by means of a filament, to a considerable distance. It is much smaller than the common leech; the largest, when at rest, not being more than half an inch long, and may be extended till it becomes a fine string; the smaller ones are very minute. It is common in the jungles in Ceylon; Bishop Heber tells us that" the native troops on their march to Canely, suffered very severely from the bites of flying leeches, occasionally even to the loss of life or limb : their legs were covered with them, and streamed with blood."