Changes in Water, Sodium and Potassium Distribution in the Duck's Egg During Incubation

SUMMARY The concentrations of Na+ and K+ in the different parts of the incubated duck's egg were determined by flame spectrophotometry. From the weights of the various parts the total amounts of these ions and their distribution in the egg were calculated. It is argued that the subgerminal fluid is formed by active resorption of water and dissolved substances from the eggwhite by the living blastoderm and not by digestion of the yolk. Differences between fertilized and unfertilized eggs are given. During incubation the concentration of Na+ in blood, amniotic and allantoic fluids decreases while that of K+ increases. There are quite large variations in Na+ and K+ concentrations in the blood, plasma and erythrocytes of ducklings, even in successive determinations in the same animal. The blood of ducklings during the first nine months of life has a higher Na+ and a lower K+ level than the blood during the later stages of the embryonic life. Data for the daily growth of the embryo and for the amounts of amniotic and allantoic fluids are given.