The mandibular organs of the cr ayfish(Procambarus clarkii)are in pairs , These yellow or gans ar e located at the dorsa of the paird mandibles , outside bases of mandibular chit inous tendons .Abundant hemolymph vessels and blood sinuses could be seen in the mandibular organ , the mandibular organ cells ar ranged in cords and surr ounded the blood sinuses .The most dist inguishing features of the typical mandibular organ cells are as follows :(1)The mitochondria and the smooth endoplasmic ret icula are dispersed extensively in the cytoplasma , and the smooth endoplasmic r eticulm occurs in two dist inct forms : cisternal and tubular .(2)The plasma membrane invaginates into cytoplasma and exhibi ts varying degrees of convolution .(3)The basal membr ane outside the plasma membrane is rich in microfilaments and thick .In the vacuola ted mandibular or gan cells , the smooth endoplasmic re ticula almost disappear , the thicken st ructures of mi tochondr ia change and the heterchromatins in the nuclear f orm a cycle near the nucle ar membrane .These modifications indicate th at the synthet ic capacity of cells causes a change , showing a state of cell pr oducts af ter se cre tion .