Page:The Zoologist, 4th series, vol 3 (1899).djvu/124

100 bivalve—some species of Sphærium or Pisidium. One of these molluscs had closed its valves upon the inner finger of one of the fore limbs, while another held tightly by the middle toe of one of the hind feet. Yet, seriously impeded as its movements must have been, the Toad was still able to swim after a sorry fashion.

At the same time and place I noticed a very small male which had only one hind leg; all the bones of the corresponding limb were apparently wanting, but the foot was present, though smaller than its fellow, and attached to the trunk by the skin alone.

Our Common Toad has a habit of swimming with the hind legs alone, keeping the fore legs or arms pressed against the sides. The Fire-bellied Frog (Bombinator igneus) often adopts the same method.

The casting of the skin frequently takes place soon after the arrival of these batrachians at their breeding places in early spring, but whether the operation is always performed at this season I do not know. In the year 1882, I noticed two females in the water casting their skin on March 20th; and in the following year met with another female thus engaged in April. I have never been so fortunate as to detect a male in the act.

The tadpoles of both Frogs and Toads are excellent scavengers, and the vast numbers which literally blacken the water of many ponds and ditches must be of great use in keeping it pure and wholesome. Decaying matter of almost any sort, animal or vegetable, is greedily devoured by them. I have seen them feeding on the dead bodies of Toads (possibly their own parents), Sticklebacks, and even of tadpoles, as well as on cow-dung which had dropped into the water; also on the soft parts of submerged and decaying leaves of trees and various plants, the veins being left untouched.

Instead of roaming about, as it were, at random in search of food, some degree of unity and method may sometimes be observed in the movements of these vast armies of tadpoles. In the marsh ditches, where they abound, it is not unusual to find two dense streams of them steadily travelling close alongside one another, but in opposite directions; an "up" and a "down" line, in fact, seems to be strictly maintained and adhered to, in order to prevent confusion. I once saw a number of tadpoles,