Painted Crabs.—On the reef of rocks which lies to the south of the harbour at Colombo, the beautiful little painted crabs[4783], distinguished by dark red markings on a yellow ground, may be seen all day long running nimbly in the spray, and ascending and descending in security the almost perpendicular sides of the rocks which are washed by the waves. Paddling Crabs[4784], with the hind pair of legs terminated by flattened plates to assist them in swimming, are brought up in the fishermen's nets. Hermit Crabs take possession of the deserted shells of the univalves, and crawl in pursuit of garbage along the moist beach. Prawns and shrimps furnish delicacies for the breakfast table; and the delicate little pea crab, Pontonia inflata[4791], recalls its Mediterranean congener[4792], which attracted the attention of Aristotle, from taking up its habitation in the shell of the living pinna.
ANNELIDÆ.—The marine Annelides of the island have not as yet been investigated; a cursory glance, however, amongst the stones, on the beach at Trincomalie and in the pools that afford convenient basins for examining them, would lead to the belief that the marine species are not numerous; tubicole genera, as well as some nereids, are found, but there seems to be little diversity, though it is not impossible that a closer scrutiny might be repaid by the discovery of some interesting forms.
Leeches.—Of all the plagues which beset the traveller in the rising grounds of Ceylon, the most detested are the land leeches.[4793] They are not frequent in the plains, which are too hot and dry for them; but amongst the rank vegetation in the lower ranges of the hill country, which is kept damp by frequent showers, they are found in tormenting profusion. They are terrestrial, never visiting ponds or streams. In size they are about an inch in length, and as fine as a common knitting needle; but they are capable of distension till they equal a quill in thickness, and attain a length of nearly two inches. Their structure is so flexible that they can insinuate themselves through the meshes of the finest stocking, not only seizing on the feet and ankles, but ascending to the back and throat and fastening on the tenderest parts of the body. In order to exclude them, the coffee planters, who live amongst these pests, are obliged to envelope their legs in "leech gaiters" made of closely woven cloth. The natives smear their bodies with oil, tobacco ashes, or lemon juice[4811]; the latter serving not only to stop the flow of blood, but to expedite the healing of the wounds. In moving, the land leeches have the power of planting one extremity on the earth and raising the other perpendicularly to watch for their victim. Such is their vigilance and instinct, that on the approach of a passer-by to a spot which they infest, they may be seen amongst the grass and fallen leaves on the edge of a native path, poised erect, and preparing for their attack on man and horse. On descrying their prey they advance rapidly by semi-circular strides, fixing one end firmly and arching the other forwards, till by successive advances they can lay hold of the traveller's foot, when they disengage themselves from the ground and ascend his dress in search of an aperture to enter. In these encounters the individuals in the rear of a party of travellers in the jungle invariably fare worst, as the leeches, once warned of their approach, congregate with singular celerity. Their size is so insignificant, and the wound they make is so skilfully punctured, that both are generally imperceptible, and the first intimation of their onslaught is the trickling of the blood or a chill feeling of the leech when it begins to hang heavily on the skin from being distended by its repast. Horses are driven wild by them, and stamp the ground in fury to shake them from their fetlocks, to which they hang in bloody tassels. The bare legs of the palankin bearers and coolies are a favourite resort; and, as their hands are too much engaged to be spared to pull them off, the leeches hang like bunches of grapes round their ankles; and I have seen the blood literally flowing over the ledge of a European's shoe from their innumerable bites. In healthy constitutions the wounds, if not irritated, generally heal, occasioning no other inconvenience than a slight inflammation and itching; but in those with a bad state of body, the punctures, if rubbed, are liable to degenerate into ulcers, which may lead to the loss of limb or even of life. Both Marshall and Davy mention, that during the march of troops in the mountains, when the Kandyans were in rebellion, in 1818, the soldiers, and especially the Madras sepoys, with the pioneers and coolies, suffered so severely from this cause that numbers perished.[4831]
One circumstance regarding these land leeches is remarkable and unexplained; they are helpless without moisture, and in the hills where they abound at all other times, they entirely disappear during long droughts;—yet re-appear instantaneously on the very first fall of rain; and in spots previously parched, where not one was visible an hour before, a single shower is sufficient to reproduce them in thousands, lurking beneath the decaying leaves, or striding with rapid movements across the gravel. Whence do they re-appear? Do they, too, take a "summer sleep," like the reptiles, molluscs, and tank fishes? or may they, like the Rotifera, be dried up and preserved for an indefinite period, resuming their vital activity on the mere recurrence of moisture?[4832]
Besides a species of the medicinal leech, which[4833] is found in Ceylon, nearly double the size of the European one, and with a prodigious faculty of engorging blood, there is another pest in the low country, which is a source of considerable annoyance, and often of loss, to the husbandman. This is the cattle leech[4841], which infests the stagnant pools, chiefly in the alluvial lands around the base of the mountain zone, whither the cattle resort by day, and the wild animals by night, to quench their thirst and to bathe. Lurking amongst the rank vegetation that fringes these deep pools, and hid by the broad leaves, or concealed among the stems and roots covered by the water, there are quantities of these pests in wait to attack the animals on their approach to drink. Their natural food consists of the juices of lumbrici and other invertebrata; but they generally avail themselves of the opportunity afforded by the dipping of the muzzles of the animals in the water to fasten on their nostrils, and by degrees to make their way to the deeper recesses of the nasal passages, and the mucous membranes of the throat and gullet. As many as a dozen have been found attached to the epiglottis and pharynx of a bullock, producing such irritation and submucous effusion that death has eventually ensued; and so tenacious are the leeches that even after death they retain their hold for some hours.[4851]