Abstract: This paper describes the genesis of the digestive system of the redclaw crayfish,Cherax quadricarinatus.The digestive system consists of three parts:fore-gut,mid-gut and hind-gut.The fore-gut and hind-gut origin from the ectoderm,and the mid-gut derives from the mesendodermal cell group.The fore-gut begins to form at the egg-nauplius stage and is made up by stomodaeum,esophagus and stomach;the mid-gut genesis at the egg-metanauplius stage and contains a mid-gut and a pair of hepatic rudiments;the hind-gut starts at the same time as the fore-gut to form the protodaeum which lies in the end of it.