The origin of the membranes and lytic enzymes involved in autophagy has been studied in metamorphosing insect fat body. The Golgi complex has two functions in the organelle destruction which takes place when fat body cells change their activities. (1) It gives rise to envelopes which extermalize organelles scheduled for destruction. Microbodies, mitochodria and rough endoplasmic reticulum are sequentially removed from the cytoplasm by investment in isolation membranes. During the isolating phase, isolation membranes have the same osmiophilia as the outer saccular and microvesicular components of the Golgi complex, they do not contain lytic enzymes and they are specific in their adhesion to organelles scheduled for destruction. (2) The Golgi complex gives rist to lytic enzymes. Primary lysosomes which contain acid phosphatase fuse with the isolation bodies formed from invested organelles to become autophagic vacuoles. During this lytic phase, acid phosphatase is present in the inner saccules and microvesicular components of the Golgi complex, in the primary lysosomes seen fusing with isolation bodies and in autophagic vacuoles.