Abstract
Fragments of rough endoplasmic reticulum containing polysomes bound to the membranes only at the 5' end were visualized in electron microscopic spreads from Chironomus thummi salivary gland cells. The length of the nascent protein molecules in the polysemes increased from the 5' to the 3' (free) polysome end. The data obtained disagree with the generally accepted model according to which synthesis of secretory proteins is concomitant with the protein transport across the endoplasmic membrane