[An atrial hematopoietic locus in the heart of the cave salamander (urodele amphibian)].

Lungless Salamanders of the family Plethodontidae have a reduced interatrial septum. The pulmonary vein is lacking. In these species, the septum as a membranous thin sheet attaches near the dorsal lip of the sino-atrial valve where a connective and muscular column, supporting the valve, extends its branches over the upper wall of the undivided atrial cavity where a sponge-like structure is formed. The meshes of this structure are the site of a erythropoietic activity as shown in the plates. Early stages in active reproduction are found in the external acid layer while in the basic inner layer the red cells undergo differentiation. This locus may be correlated to the particular anatomy of the heart concerning the lacking of the pulmonary vein, the position of the sino-arterial aperture shifted to the left side and the reduced interatrial septum. In the large upper cavity of the atrium a certain degree of blood stagnation could be possible which could allow the settlement of this locus. No ventricular erythropoiesis nor epicardial granulopoiesis have been found. This hemopoietic locus is lacking in the family Salamandridae and Anura.