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Engystoma Texense, Girard — Part 4
The frog shown at the left is a typical specimen. This frog is one that was found at the bottom of the fifteen-foot entrance of a drive-well. It was impossible to tell how long he had been a prisoner, but something had tamed the poor creature remarkably. He was grateful for any attention in the way of worms or grasshoppers, and sang and talked most confidingly when taken in the hand or when showered with water. Soon after being taken from his prison, and before he had been released to the good hunting-fields near at hand, he moulted the skin. The process is exactly like that described for the toad (pp. 73-75). The frog sits up very high, with his back greatly humped. After the skin is split along the back of the head, he uses the front feet to get it from over the eyes, with movements like those of a cat when washing over its ears. He looks especially ludicrous when removing the hind legs from their sheathing coasts, because of the length of the legs. They are drawn forward and then stretched back again and again during the process.
The Leopard Frogs are among the first of our frogs to come from their hibernation in the spring. (The wood frogs are likely to precede them.) The eggs are usually laid in March. (March 25, April 5, 1890. R. virescens. T. H. Morgan, Baltimore, Md. March 22, April 1, 1897. R. virescens. R. G. Harrison. "The Leopard Frog breeds in March." C. S. Brimley, Raleigh, N. C.) The shallow water of marshes and of pond and lake margins resounds with their voices during the latter half of March and in early April, just when the bluebirds are deciding which cozy hole in the old apple-tree will make the best home for a family. Even when at the height of its power, the individual voice is not loud, although it is musical. The voice defies description in terms of familiar sounds. It has lately been described as a "characteristic snoring croak or rattle."
Let us go to the marsh or pond in late March or early April. It is a warm, sunny forenoon. The maroon hoods and grey, pointed leaf-buds of the skunk-cabbage are picturesque among the moss and dead leaves. The water presents a rather desolate expanse, for it is too early for the appearance of much green. All seems silent as we approach. We walk on the firm foundation made by tangled sweet flag roots until we are at the very edge of the water. As we listen and watch, low, moaning, or grunting sounds proceed from everywhere about us. The pond is filled with Leopard Frogs. We can see their heads, with the bright eyes and distended ear-like vocal pouches protruding above the water. It is impossible to make one hear these talking voices unless he is already familiar with them. To say that the sound is low-pitched, throaty, and vibrant does not bring it to one's ears. The sounds are produced both by the male and by the female. Either will make the sounds when taken into the hand.
The eggs are laid in masses in the shallow water. They may be attached to sticks and grasses or left free in the water. Those drawn and described were laid on the morning of April 9th by a frog brought from the pond two days previous. They were attached to a fern leaf that bent over the water. The whole laying was in one mass about five inches in diameter and two and a half inches thick, which contained between five thousand and six thousand eggs. Each egg is very small (1 1/2 mm. in diameter) and velvety black in colour. The eggs are so close together that the entire mass is dark-coloured, notwithstanding the fact that each is surrounded by a perfectly transparent sphere of gelatinous substance-three concentric spheres, in fact. This substance is so transparent that it does not prevent our watching the process of development. If we look closely at the eggs, we discover that they are black above only, and that the lower side--about one-third of the entire surface--is creamy white in colour. The egg contains not only the germ of the future frog, but yolk for its growth. The white lower part of the egg consists wholly of this food yolk.