_H. versicolor_ is one of the most delicately coloured species of Eastern North America, extending northwards into Canada. It is about 2 inches long. Its colour passes within a short time from dark brown or olive grey to pale delicate grey, almost white, occasionally retaining a few large darker patches on the back, and delicate cross-bars on the limbs. A small portion of the sides and the posterior part of the belly are bright yellow. The skin is granular, owing to the presence of small warts which produce an acrid secretion. It is said to be found in trees, or about old stone fences overgrown with lichens, the colour of which it resembles to perfection. It becomes very noisy towards the evening, in cloudy weather or before rain, the voice consisting of a liquid note, terminating abruptly, like "l-l-l-l-luk." My own captives fully bear out this statement of Holbrook's. Settled motionless during the day upon a piece of bark in a shady {195}corner, but occasionally uttering the quaint and rather faint note, they become very lively in the evening, catching insects by long jumps, or investigating the hollows of decaying mossy stumps. Their general colour is then spotless, almost silvery grey. In the day-time they are sometimes suffused with delicate green. The propagation has been studied by Miss M. H. Hinckley.[85] They pair in shallow pools, in Massachusetts, in May. On the 10th of that month eggs were attached singly, and in groups, on the grasses resting upon the surface of the water; first drab-coloured, they became lighter in a few hours. Some larvae escaped from the gelatinous envelopes on the following day, the others on the third day; they clung to the grasses by means of their prominent suckers. The head and body were cream-coloured, with olive dots, and averaged ¼ inch in length. Gills appeared on the fourth day, to disappear again during the four following days, first those of the right, then those of the left, side; the suckers became less conspicuous, and the general colour turned into deep olive-green, with fine golden dots on the upper and lower surfaces. The eyes were of a brilliant flame-colour. On the eleventh day the suckers or "holders" had disappeared, and the hind-limbs were indicated by small white buds. By June 5th, _i.e._ the twenty-seventh day, the toes developed the terminal discs; the mottling of gold had given way to a uniform olive or pea-green. Movements of the future arms beneath the skin appeared on the 28th of June, at the age of seven weeks. The arms, mostly the right one first, were thrust out on the 2nd of July; the fins of the tail were absorbed rapidly, and towards the end of the seventh week the nearly transformed creatures began to leave the water. The young frogs changed colour rapidly, in adaptation to their surroundings, but the four specimens which survived were never all found to be of the same colour during the next three months. They first lived upon Aphides, later upon