. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 446 KEN YON S. TWEEDELL centrifugation, the astral granules being derived from a layer that is coincident with the mitochondria in Pectinaria. This is not the case in Spisula. In electron microscope studies, Rebhun (1960) identified the metachromatic granules as multivesicular bodies and concluded that the metachromatic granules were definitely not lipid, mitochondrial, yolk or cortical granules. Two other com- ponents were present, the Golgi bodies, particularly plentiful in early oocytes, and annulate lamellae which occasi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 446 KEN YON S. TWEEDELL centrifugation, the astral granules being derived from a layer that is coincident with the mitochondria in Pectinaria. This is not the case in Spisula. In electron microscope studies, Rebhun (1960) identified the metachromatic granules as multivesicular bodies and concluded that the metachromatic granules were definitely not lipid, mitochondrial, yolk or cortical granules. Two other com- ponents were present, the Golgi bodies, particularly plentiful in early oocytes, and annulate lamellae which occasionally orientated with the asters. It is possible that one of these particles is analogous to the astral granules of Pectinaria. The nucleolus of the mature oocyte of Pectinaria, characteristically an amphinu- cleolus, was strongly basophilic in the cortical region but the nucleolar vacuoles re- mained unstained (Fig. 26). All of the vital dyes and fluorochromes applied to the oocytes indicated that the body of the amphinucleolus was principally composed of DNA. This was confirmed after treatment of the fixed eggs with the Feulgen. FIGURE 26. A centrifuged immature oocyte, showing particle distribution in relation to the intact germinal vesicle. 1, Fat droplets. 2, Lipid granular cap. 3, Hyaline zone. 4, Germinal vesicle substance. 5, Basophilia. 6, Amphinucleolus. 7, Granular Band I. 8, Granular Band II, mitochondria and proteid yolk. 9, Dense proteid yolk. 10, Centrifugal vacuole. reagent. When the eggs were previously extracted with 4% trichloracetic acid at 90° for 15 minutes, the nucleolus remained unstained following the Feulgen test. Kobayashi (1953, 1954) observed similar amphinucleoli in the eggs of the oyster (Ostrea lapcrousi} which were Feulgen-positive. He also found that the karyosome stained with methyl green and the plasmosome with pyronin, indicating the presence of RNA. Another type of amphinucleolus was reported by Sawada and Murakami (1959) in Mactra veueri
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