Ovaries from the spider crab, Libinia emarginata L. were studied to learn more of vitellogenesis in crustaceans. Oogonia and previtellogenic oocytes were found in the core of the ovaries. Vitellogenic oocytes are located more peripherally. Profiles of the endoplasmic reticulum are abundant in the vitellogenic oocytes. The granular and agranular reticulum as well as the Golgi complex are active in yolk synthesis. As vitellogenesis proceeds, yolk precursors are incorporated into the egg by micropinocytosis at the egg surface. Thus, in Libinia, yolk materials appear to be derived from both intra-and extraoocytic sources.

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Morphological aspects of nucleoli of iris epithelial cells participating in W o m a n lens regeneration in the adult newt (T.riturus viridescens) were studied with electron and phasecontrast microscopes at various times after lens removal. In normal condition, the nucleoli appear as small, compact bodies composed of fibrous elements. The granular element is often lacking, but when present, is sparse and 10-cated at the periphery of the organelle. Within two days after lens removal, the size of the nucleolus increases, and its shape becomes complex and diversified. The granular element increases in absolute as well as relative amount. Granular and fibrous components become intermingled and together form the fibrogranular region. Portions of this region often project from the nucleolus as coarse threadlike extensions that become a prominent feature. Morphogenesis of the organelle continues during the subsequent two days. In parallel with these structural changes, the number of nucleoli per nucleus and the frequency of nuclei containing nucleoli increases. All these changes start in the nondividing phase of the iris epithelium before induced cell division. These changes in nucleoli are the earliest so far observed in iris epithelial cells after lens removal, and coincide in time with the activation of ribosomal RNA synthesis previously observed in this system.Complete removal of the lens from the adult newt eye is consistently followed by DNA replication in the iris epithelial cells (Reyer, '66; Eisenberg and Yamada, '66), which do not replicate DNA in the normal condition (Yamada and Roesel, '69). Labeling of cells with [3H] thymidine becomes detectable three days after lens removal and attains the 25% level two days later. This DNA replication is preceded by activation of ribosomal RNA (rRNA) synthesis, which can be demonstrated within two days after lens removal (Reese et al., '69). These events prelude depigmentation and subsequent differentiation into lens cells from the ins cell population (Yamada, '67 for review).A substantial body of evidence from biochemistry and genetics indicates that the precursor of rRNA is synthesized in the nucleolus, or in the chromatin associated with it, and processed in the nucleolus (Birnstiel et al., '66; Brown, '67; Brown and Gurdon, '64; Brown and Littna, '64; Perry, '67; Willems et al., '68). Cytologic studies (Granboulan and Granboulan, '65; Karasaki, '65; Miller and Beatty, '69)

The localization of acid phosphatase in the telotrophic ovary of the water strider, Gerris remigis, has been studied by light microscopy, utilizing a simultaneous coupling azo dye technique on frozen sections. The enzyme is demonstrable in the cytoplasm of advanced nurse cells, and to a variable degree in the trophic core.Reactivity is also distributed throughout the cytoplasm of young (germarial) oocytes.As oocytes enlarge and pass into the vitellarium, reactivity becomes confined to a peripheral band, which widens and becomes associated with a peripheral accumulation of preyolk bodies. This reactivity disappears from the ooplasm before vitellogenesis is entirely completed. Oocytes which undergo degeneration before completing maturation display large, internal, phosphatase-reactive areas. Acid phosphatase is first demonstrable in follicle cells at the onset of vitellogenesis. Variations in its intensity and intracellular localization are in conformity with previous suggestions in the literature that follicle cells are implicated in vitellogenesis and in subsequent chorion elaboration. Following ovulation, the follicle cells become intensely reactive and as they degenerate, some of this reactive material is expelled from the ovary through the follicle cell basal surfaces. Reactive residues accumulate in the yellow body at the base of the ovary. Thus the enzyme localization is corzelated with physiological autolysis in nurse cells and post-ovulatory follicle cells and with pathological autolysis in oocytes. Its localization in normally developing oocytes and follicle cells suggests involvement in the process of vitellogenesis and chorion formation as well.

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