[in Japanese]

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 The aim of this work is to clarify the developmental mechanisms of the enamel structures (histogenesis) on the phylogeny, which is realized by the cytological and the histological background. On the animal evolution, the tooth developmental mechanism is essentially to analyze for to clarify the calcification, because the tooth enamel composed of about 95% over inorganic matrix, and the tooth morphology is based on the calcification.
 On the enamel evolution, Hunter-Schreger band develops from a simple island patter to complex patterns with every species has own individuality. The enamel prism arrangement and course also evolve from a simple to complex types along with the phylogeny. These prism courses in Schreger bands are classified into 5 types (two of convergence and three of divergence) by 150 species of fossil and recent animal enamels. This phenomenon suggests the enamel structures are formed by the grouping ameloblast and the cell mobility. The author proposes the mobility, as the hypothesis of ameloblast ‘Grouping and Dancing’ . These mobilities are prove by the tooth development and the immunohistochemistry on next points; 1) The correlation between the ameloblasts and the enamel crystals (calcification), 2) The direct relationship between the ameloblast and the enamel structure, 3) The origin and development of Ameloblast ‘Grouping and Dancing’ , 4) Is there Ameloblast ‘Grouping and Dancing’ .
 1) Calcification. The enamel crystal seeds and develops in enamelins, which forms the nano-tube (Nano-space theory). The tube arranges almost perpendicular against the cell membrane of Tomes process with the affinity. Thus the crystal orientation is decided. The organic matrix of enamel is dissolved and the crystal growing space increases and regulates the crystal form.
 2) Relationship between ameloblasts and enamel structures. It is observed both the enamel and the ameloblast as double layer in the thick (about 50 or more) and almost tangential sections against the enamel and the ameloblast. Each ameloblast group corresponds to a zone of Schreger bands on the developing enamel. Those grouped ameloblasts is a part of clusters of the enamel organ from the outer enamel epithelium to the ameloblast. It suggests the whole enamel organ harmonically moves with ‘Grouping and Dancing’ .
 3) The development of ‘Grouping and Dancing’ . The initial group arises in the early developing inner enamel epithelium. The stratum intermedium cells develop on these mass of the inner enamel epithelium cell (ameloblasts) and connects to the outer enamel epithelium cell groups through newly developed enamel cords. These show the group is associated with other cells of whole enamel organ, which has the harmonical mobility with ‘Grouping and Dancing’ .
 4) ‘Grouping and Dancing’. The anti-actin reaction is clearly provides the ameloblast groups which corresponds to zone of Schreger bands. Some cell masses have no-reaction against the anti-actin. The anti-actin reaction cell groups differents from anti-Keratin reacted cell groups on the enamel organ. There are also no reacted cell groups against the keratin. These suggest the keratin and the actin alternately and rhythmically changes the reaction in the enamel organ. Tubulin reacts all ameloblast layer avoid of some ameloblasts and Tomes processes. This also suggests the ameloblast plays the periodical and rhythmical secretion. Desmoplakin reaction shows from the stratum intermedium side of the ameloblast layer to the outer enamel epithelium. It shows these areas softly fixes from the enamel organ mobility.
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 Molluscan shell consists of complicated structure called shell microstructure, which is composed of two polymorphisms of calcium carbonate crystals, aragonite and the calcite together with a tiny amount of the organic matrix (OM) secreted from the mantle tissue. Experiments have been conducted specifically to investigate the nacreous layer, which mainly comprises aragonite, and has a specific geometry, in order to gain an understanding of the effect of OM on shell formation. Several hypotheses of the nacreous structure formation have been demonstrated such as the compartment hypotheses (Bevelander & Nakahara, 1969), the template hypotheses (Degens, 1976, Weiner, 1979) and the epitaxy hypotheses (Neuman & Neuman, 1958, Crenshaw & Ristedt, 1976, Wada, 1980). In contrast to the nacreous layer, information about mineralization of the calcitic foliated layer is very limited. In spite of the recent report on the genes encoding the OM components in the foliated layer (Sarashina and Endo, 2001; Samata et al., in press), the process of the foliated layer formation is left a matter open.
 In the present study, we attempted to elucidate the process of the microstructure formation of the foliated layer, focusing on the function of the specific molecules in the oyster organic matrix by in vitro crystallization experiment. After decalcification by acetic acid, the soluble and insoluble organic matrices were extracted from the foliated layer of C. nippona. The insoluble organic fraction was further treated by alkaline and 2-mercaptoethanol, resulting in separation of the mercaptoethanol soluble fraction (MESM).
 The crystallization experiment was performed by adding OM components in the supersaturated crystallizing solution. When the MESM and the WISM were added to the crystallizing solution, calcite crystals with similar morphology of thin plate to those of the foliated layer of C. nippona were inducted on the WISM.
 These results may present new concepts that we think may well have implications to the biomineralization process of oyster shell.

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 Molluscan shell is mainly composed of CaCO₃ crystal with little amount of organic matrix (OM). Carbonic anhydrase (CA) is thought to be one of the most important enzyme for molluscan shell formation which catalyzes interaction between CO₂ and HCO₃^-. Nacrein is the main component in the soluble organic matrix (SM) protein in the nacreous layer of Pinctada fucata cultured in Japan (Japanese pearl oyster), which contains two functional domains one is a carbonic anhydrase-like doman (CA domain) and another is a repeat sequence domain rich in Asn and Gly (NG-repeat domain).
 In this paper showed tertiary structure of nacrein inferred by Small Angle X-Ray Scattering, Tertiary structure analysis of nacrein by using the Small Angle X-ray Scattering resulted in calculated molecular weight of nacrein approximately 47kDa and inferred form of it as “S-model”.

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 Molluscan shell comprises two types of crystals, aragonite or calcite, which are arranged to form various shell microstructures. Shell of Pinctada fucata is divided into two microstructures, an aragonitic nacreous layer and a calcitic prismatic layer. It is widely believed that organic matrix (OM) is involved in regulation and control of both the crystal polymorphism and shell microstructure (Watabe and Wilbur, 1960; Lowenstam, 1981; Weiner, 1984). Analyses of genes enoding OM-proteins have been carried out those in nacreous layer of pearl oyster because of its industrial value, and as a result, Nacrein, N 16, MSI60 have been identified. Meanwhile, in recent years, MSI31 and Plismalin 14 have been identified in prismatic layer. The mechanism of molluscan shell formation is still unclear, even in case of P. fucata. Particularly, the mechanism about the crystallization of aragonite or calcite in the alternative is left unsolved.
 Based on preliminary biochemical analyses of OM proteins in both the nacreous and prismatic layers in the P. fucata shell, Samata (unpublished data) identified and characterized the N-terminal amino acid sequences of several components unknown to date. Present study is conducted in order to identify primary structure of one of these components with approximate size of 35 kDa by cDNA cloning.
 Consequently, approximately 2 kb nucleotide fragment estimated as a part of an open reading frame (ORF), was amplified and sequenced. Amino acid composition of the novel protein was rich in glycine and alanine and scarce in acidic amino acids. These features have not been reported in other OMs in molluscan shells.
 Further analyses of gene expression and protein function will open a new insight into shell formation mechanism of pearl oyster.

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 Misasa Hot Springs in Tottori Prefecture is known as one of hot springs in which concentration of high radium (Ra) and radon (Rn) are very high. Especially ²²⁶Ra is highly contained in the microbial mats consist of mainly ferrihydrite compound. The accumulation of radioactive elements by microorganisms was examined by optical microscopy, EDXRF, AAS, SEM, and TEM observations in combination of STEM-EDS. In the green parts of microbial mats, ferrihydrite and calcite are formed by increasing pH and dissolved oxygen (DO) induced by photosynthesis of cyanobacteria, such as Oscillatioria spp. and Phomidium spp., suggesting the ²²⁶Ra is adsorbed to cyanobacterial cells. Whereas, coccus and bacillus typed bacteria are found in reddish brown parts under beneath. Observation by TEM of the ultra thin section of the cells showed that the bacteria produced extracellular polymers around the cell wall and capsules, cause embedding of granule ferrihydrite and calcite. The cells tended to be adsorbed highly ²²⁶ Ra on the capsule and slime layer of bacterium, because they contain negatively charged carboxylate in rich. The interactions among the cells, ferrihydrite and ²²⁶Ra contribute to environmental factors influencing the biomineralization processes. The radioactive elements at microbial mats were able to support the growth of resistant bacteria to enable bioremediation.

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 Specimens of the fossil teeth and bones of Palaeoloxodon naumanni, Proboscidea, collected from the Middle Pleistocene Hamamatsu Formation are reexamined and described. Although these specimens are very important in terms of the objects recovered from the same area and the same geological horizon as the holotype specimen of this species, they have not been described exactly until now.
 Of the specimens described, a triquetral bone, a capitate bone and a patella are almost complete specimens. Compared with the Asian elephant, the triquetral bone is more flat in proximal-distal section, the articular surface with the fifth metatarsal is bigger, and it is tilting further to the lateral side. On the capitate bone, the cranial-caudal length is longer than the lateral-medial length, and the caudal process is well-developed. These characters are similar to those of typical P. naumanni. After comparing the patella with the specimens occurred from the other areas, it is clear that bigger specimens are relatively longer in the proximal-distal section.

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