Pleurodeles waltlii is reared in many aquaria and its eggs are used for experimental embryological work. Embryologists have, however, been handicapped by the lack of accurate studies of the development and morphology of its chondrocranium. A study of the developing chondrocranium of Pleurodeles waltlii of six different developmental stages has therefore been carried out. The youngest stage used was 38 (Gallien and Durochet, '57) and the oldest was of a specimen at the end of metamorphosis. MATERIAL AND METHODSThree larvae of each of the six stages were fixed in Zenker's solution and decalcified in 1:6 Na-formate and formic acid. The heads were embedded in paraffin, serially sectioned, at 10 N and stained with azan. From each stage one larva was chosen for a graphic reconstruction of the chondrocranium. The reconstructions were carried out according to Pussey's method ('36) by using the drawings of eveiy second section at an enlargement of 50. Stage A (figs. 1 ; 2 ) Total length of larva 10 m m ; length without tail -6 m m The chondrocranium of this stage is comprised mainly of two symmetrical relatively large cartilaginous complexes (fig. 1). Each of these complexes is composed of a trabecula, which appears from the first to be continuous with the dorsal orbital cartilage (fig. 2) by means of an anterior preoptic root and a posterior pila antotica, between which the foramina for the second and third nerves are enclosed separated from each other by the pila metoptica. The fourth nerve passes dor-J. MORPH., 114: m -s m