الفهرس 
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Abstract
The current study was conducted on 80 grass carp fish at different developing stages starting from the (1- 4-10 -20) days post hatching larvae, (59 dph fingerlings) and (90- 365 days juvenile fish) till the adult stage. Grass carp larvae and juveniles were collected from the fish hatchery of the central laboratory for aquaculture. The adult fish were collected from El-Abbassa fish farm. All samples were examined to compare the results and to observe the developmental differences of the liver and pancreas during these stages. At the early post hatching stages, the hepatic primordium was observed dorsal to the yolk sac. While the pancreatic cells were determined dorsal to the developing gut tube. They appeared nearly similar to the hepatocytes so, it was difficult to distinguish them at first day post hatching (dph). At 10 dph the yolk sac was completely absorbed. The hepatocytes are differentiated than that of the previous stages. They are arranged in plates separated by hepatic sinusoids. while, at 20 dph the liver was increased in size and number of differentiated hepatocytes. the pancreatic cells appeared on the periphery of the liver some of them began to penetrate the hepatic parenchyma along with the portal vein branches. They differentiated into two cell types: the exocrine and the endocrine pancreatic cells. They were frequently determined among the adipocytes of the intestinal mesentery. Also, the exocrine cells were detected within the mesentery as well as diffused in the hepatic and splenic parenchyma. At advanced stages the adult hepatocytes have the criteria of active cells that increased in size and number. In addition to high number of zymogen granules were detected within the cytoplasm of the pancreatic acini. The amount of fat and glycogen was also increased within the cytoplasm of the hepatocytes. The results were examined by the light and electron microscope (SEM, TEM).