DEVELOPMENT OF THE ORAL DISC IN EMBRYOS AND LARVAE OF THE EUROPEAN TREE FROG, HYLA-ARBOREA

The mouth of the tree frog Hyla arborea started to form during stage 2 1, at the age of 3-4 days. In stage 24, horny tablets appeared. The la rval period began with the stage 25, when the first horny teeth appear ed. During the larval period, the number of horny labial teeth as well as labiaI papillae increased. In stage 26, the dental formula complet ed as I:1-1/III and persisted as such until stage 41, when metamorphos is of the oral disc started. The variation of the dental formula I:1-1 /1-1:II was at 20% of the total number of the observed exemplars. Subs equently, the larval mouth structures resorbed and small adult-like ja ws developed.