AbstractCytoplasmic synthetic organelles (Golgi complexes, polysomes, and rough and smooth endoplasmic reticulum) are present in most photoreceptor cells of the crayfish retina in winter throughout the late‐night 24:00 to 06:00 h period. These same retinular cells contain few or no lysosome‐like bodies. There is no evidence for autophagic receptor membrane breakdown even during the degradative phase (24:00 to 02:00 h) of the late‐night quadrant.The fine structure of rhabdom microvillus bases and their continuity with retinular cell somata and endoplasmic reticulum differ characteristically in each of the three successive turnover phases between 24:00 and 06:00 h. Typical stalked attachment of microvillus clusters to retinular cell bodies is resumed by 06:00 h.A minority of retinulas are severely abnormal. Their rhabdoms are shorter and closer to the basement membrane while their receptor cell nuclei have descended proximally. During the degradative phase, the retinular somata may lack synthetic organelles altogether while their rhabdoms are disorganized, detached from their parent cytoplasm, and occasionally invaded by hemocytes. In contrast, synthetic organelles are numerous in the cytoplasm during the late synthetic phase (03:00 to 04:00 h) when photoreceptor membranes are less disrupted and cytoplasmic bridges between rhabdoms and cell bodies are intact.Both moderate late‐night degradation of the rhabdom and the less frequent catastrophic breakdown seem to be mediated by extracellular lysozymes provided in part by retinal hemocytes. Acid phosphatase localization at the beginning of the degradative phase (24:00 to 00:30 h) demonstrates that invasive granulocytes are a primary source of this enzyme. Another hemocyte function previously hypothesized is proven here by finding phagocytized fragments of rhabdom and other retinal elements in most of the retinal macrophages during late‐night synthetic and resting phases.