Fig. 2.

Multilayered glial membranes in swsmutant brains as seen in EM horizontal sections. A, D, G, Wild type. A, Retina and lamina.D, Cell bodies of the lamina cortex, showing a glial cell recognizable by its dark cytoplasm. Extensions of the glial cell surround various neurons with single-layered wrappings.G, Medulla neuropil, a tangle of synapses. B, E, H, In newly eclosed sws¹flies, glial processes form multiple sheaths around neurons in the cortex (arrows in B, inset inE) and around axons in the neuropil (arrow inH). C–I, In 7-d-oldsws¹ flies, large membrane whorls are visible (F, I). These are especially prominent in the lamina cortex (arrows in C). Flies were kept at 25°C. Re, Retina, La, lamina; G, glial cell; N, neuron;A, axon. Scale bars: A–C, 3 μm;D–I, 0.5 μm.