Relative Weight of Meso and Metanephros

1. The acid and alkaline phosphatase activity of the mesonephros increases from the 4th to the 16th day, decreasing from then onwards. 2. The acid and alkaline phosphatase activity of the metanephros increases from the n t h to the 16th day, decreasing slowly to the 20th day. A rapid rise is observed after hatching. 3. The alkaline phosphatase activity that is diffusely located in the cells of recently formed secretory tubules of the mesoand metanephros polarizes to the brush border zone later on. 4. Ribonuclease-removable basiphilia, abundant in the mesonephric tubules up to the 6th day of incubation, decreases from then onwards. 5. The metanephric blastema and tubules present a high concentration of ribonuclease-removable basiphilia up to the 13th day. From then on its content decreases in the whole organ with the exception of certain groups of cells still in differentiation.