Figure 4. Fluorescence micrograph of a vitellogenic follicle that had been exposed in situ to fluorescein-labeled rabbit serum globulin. The probe had been injected into the hemolymph of a pharate adult Hyalophora female. Fluorescence is present in a continuous zone of protein yolk spheres that had been produced during a 24 hour incubation. The labeled yolk spheres had not mixed with the cohesive core of non-fluorescent yolk spheres that had been produced prior to injection of the probe. The follicle was frozen and sectioned in a droplet of hemolymph whose fluorescence is visible on the lower right.