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Show 1895.] OF SOME TBEE-FEOGS OF BEAZIL. 91 surrounded by a wall of mud-nurseries for the tadpoles. Nine of these nests or pools may be seen on the figure, and I shall describe how we witnessed their formation and subsequent use. For the purpose of cleaning and deepening, the pond had been nearly emptied the year before and was kept in this state till the beginning of 1894, the water in the centre being no more than from 3 to 4 feet deep. In the first days of February we noticed some newly made walled pools every morning. W e had to wait for full moonlight to make our observations. On the night of the 18th February, between 9 and 11 o'clock, we approached the pond, occupied, as we could hear from a distance, by at least a dozen of the large Tree-Frogs. The moon was shining brightly, and much favoured our undertaking, but even under these circumstances we had to accustom our sight to discern the details in the margiual vegetation and the portions somewhat hidden in the shadow. By and by we discovered the " ferreiros," some at work, others drumming together on the walls of some pool or in the middle of the pond, sitting upon some floating object, such as water-plants. The vocalists, the moderately inflated subgular vocal sacs of which w e could distinguish, were males. W e were posted on the side where the nests nos. 1 to 5 are to be seen. From a distance not greater than 2 to 3 feet we could survey, with all desirable distinctness, the rising of nest no. 3. O n that place w e first saw some slight movement in the water, produced by something stirring below the surface. W e then soon saw a mass of mud rising to the surface carried by a Tree-Frog, of which no more than the two hands emerged. Diving again, after a moment's time, the frog brought up a second mass of mud, near the first. This was repeated many times, the result being the gradual erection of a circular wall. From time to time the builder's head and front part of body appeared suddenly with a load of m u d on some opposite point. But what astonished us in the highest degree was the manner in which it used its hands for smoothing the inside of the m u d wall, as would a mason with his trowel. And by examining the hands of Hyla faber it will readily be understood that they must act as excellent trowels, the terminal phalanges supporting very large expansions. This careful smoothening could be better observed as the wall got higher, until it reached about four inches, and the Tree-Frog was then obliged to get out of the water. The parapet of the wall receives the same careful smoothening, but the outside is neglected. The levelling of the bottom is obtained by the action of the lower surface (belly and throat principally) together with that of the hands. W e can well compare the aspect of the pool to the crater of an extinct volcano or a large porringer filled with water, measuring nearly a foot in diameter and generally of a very regular circular form. N o w we have to record another observation, made with the most positive certainty, viz., that the male frog is present during |