Nuclear volumes and DNA in Tilapia melanopleura (Duméril) Hepatocytes during postembryonic development. - During postembryonic development in Tilapia melanopleura (Duméril) there is a halving of the nuclear size in liver cells. The DNA content in these nuclei, as determined by cytophotometry, is unchanged, and the reduction in nuclear size is thus to be related to variations in protein content. Some considerations are made on the possible biochemical basis of this reduction on nuclear sizes, that is compared to the type of divisions that occurs in segmenting blastomeres.