It was long a matter of dispute as to whether leeches were produced from eggs or born alive, but it is now ascertained that the ova are developed in a singular case, having some resemblance to the cocoon of a silkworm. The following engraving represents this case, of its natural size: [fig. 1], shows the perfect case or cocoon, and [fig. 2], the same opened, with the young leeches contained within it; it is said that, at times, there are as many as thirteen or fourteen in one case. This cocoon is formed by the parent animal, and by it deposited in the mud or clay, which composes the bed of the pool it inhabits.
The fact of the young leech being produced from these cocoons, although only latterly ascertained by naturalists, was long since well-known to the dealers in leeches on the French coast, who avail themselves of this knowledge of their habits, to multiply them for the purpose of sale.
“It was by these means the leech-dealers of Bretagne, and particularly in Finisterre, replenished the ponds in which they preserved those leeches which were intended for the Paris market.
“About the month of April or May, according to the nature of the season, they send out labourers, provided with spades and baskets, to the little muddy marshes, where they are known to exist in abundance. These workmen then set about removing those portions of mud that are known to contain cocoons, which are afterwards deposited in sheets of water previously prepared for their reception; here the young leeches quit the cocoons, and are allowed to remain for six months, when they are removed to larger ponds.” While they remain in these ponds, the cattle and other animals are driven to the water, for the purpose of allowing the young to feed upon them, as it is supposed that they grow much more rapidly after having partaken of blood.
There is a small species of leech in the island of Ceylon, which is more dreaded, and, from its great numbers, produces more evil, than even the venomous reptiles which are found in the island, including the terrible hooded snake itself.
The largest of these leeches are seldom more than half an inch in length, and the smallest are minute indeed. This leech is a very active animal; it moves with great rapidity, and is even said occasionally to spring. It is supposed to have an acute sense of smelling, for no sooner does a person stop where leeches abound, that they appear to crowd eagerly to the spot from all quarters. In rainy weather, it is shocking to see the legs of men on a long march thickly beset with these creatures, gorged with blood, and the blood itself trickling down in streams. It might be supposed there be little difficulty in keeping them off; but they crowd to the attack, and fasten on more quickly than they can be removed. Their bites are much more troublesome than would be imagined, being very apt to fester and become sores, and, in persons of a bad habit of body, to degenerate into extensive ulcers, and ultimately cause the loss of a limb, if not that of life itself.
Many plans have, of course, been resorted to, to avoid this pest, such as anointing the legs with tobacco-water, grease, &c., but all to very little purpose, the only successful mode appearing to be, the enclosing the lower part of the legs in boots and pantaloons, fitting very closely to the limb, a very unpleasant dress in so sultry a climate.