A study was made of age variation in the size and enamel patterns of the third upper molar of 99 Eothenomys smithii specimens from Japan. No significant age variation was found in either the frequency of the patterns, or the width of the dentine confluent space between the second and the third triangles. Deep lingual reentrant folds, on the posterior loop, appear in specimens where the condylobasal length (CBL) is of 22-24 mm, then the pattern with a shallow reentrant fold increases in frequency in larger CBL classes. The depth of the inner fold showed the same tendency as the changes in the patterns. A significant association, however, between five enamel patterns and age classes, depends on classification according to CBL or body weight. This proved insignificant in five CBL classes, but significant in three CBL or body weight classes. A gradual transition in the age variation of the posterior loop patterns was found among Eothenomys species which have rootless molars throughout life. The simple enamel pattern form significantly increased in frequency with advancing age in E. andersoni and E. shanseius, resembling Clethrionomys glareolus and C. rufocanus ; on the other hand, in E. regulus, E. inez, E. eva, E. chinensis, E. wardi, E. custos and E. proditor no age variation was found on the posterior loop, thus resembling Microtus pennsylvanicus. E. smithii shows a little age variation in the enamel patterns, the variation of which is of an intermediate type.

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Restriction fragment length polymorphisms (RFLPs) in nuclear ribosomal DNA (rDNA) spacers and mitochondrial DNA (mtDNA) were examined in red-backed voles collected in Hokkaido (Japan), and Korea. These voles have been classified into six species on the basis of morphological characteristics, such as dental morphology. The RFLPs of the rDNA allowed us to classify the voles into three distinct groups : rCrt (Clethrionomys rutilus), rCrf (C. rufocanus, C. sikotanensis and Eothenomys regulus) and rCrx (C. rex and C. montanus). The estimated sequence divergence between rCrt and rCrf and that between rCrf and rCrx were 4.8% and 2.3%, respectively. In the rCrf group, no major differences in mtDNA were observed among the populations from the mainland of Hokkaido, Rishiri Island, and Daikoku Islet. Similarly, in the rCrx group, mtDNA haplotypes from the mainland of Hokkaido and Rishiri I. were closely related each other, indicating that there have been genetic exchanges between the populations after speciation, or those haplotypes are derived from recent common origin. The Korean red-backed vole, which is sometimes referred to E. regulus, had rDNA identical to that of the rCrf group from Hokkaido. By contrast, the mtDNA haplotype of the Korean vole was substantially different from that of C. rufocanus in Hokkaido (8% sequence divergence). These results imply that the Korean red-backed vole and C. rufocanus in Hokkaido are very closely related and that ancestrally diverged mtDNA haplotypes have been maintained in the different geographic regions.

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The home ranges and habitat preferences of female sika deer (Cervus nippon) on Nozaki Island, in the Goto Archipelago were studied by radio-tracking. Six radio-tagged females were tracked continuously during June, August, October and December 1991. Female deer remained in small home ranges including both open and forest habitats throughout the year. These ranges overlapped to a considerable extent, however, individuals moved independently of each other. The females tended to select open habitats from spring to autumn and forest habitats in winter.

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An examination was made of the distribution of cardiac musculature in the pulmonary venous wall of three Mustela species (ermine, American mink and ferret) of different body size. Only the ermine possessed cardiac myocytes in the tunica media of the intrapulmonary venous walls continuing from the left atrium, whereas the two other species had the musculature restricted to the large extrapulmonary vein. The distribution of the musculature is thought to depend on the body weight and heart rate of various species. These findings confirm the supposition that, whereas smaller mammals have more extensive cardiac musculature, even in the intrapulmonary venous wall, in order to regulate venous blood return and to resist reflux resulting from frequent atrial systole, the larger species may not require cardiac musculature in the distal vein.

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The gait of several extant mammals was analyzed so as to provide basic data for the restoration of the terrestrial locomotion of extinct animals. An attempt has been made to establish the correlation between the gaits and the morphological data, as the latter can be obtained even from fossils. Animals walking naturally were recorded on videotape, appropriate frames were then printed for analysis. Five kinds of gaits are illustrated here with supporting graphs. In addition, some diagrams were drawn using variables of the gait cycle, the rhythm of limb work, the rhythm of locomotion and the hindlimb length ratio to the trunk. Changes in the four joint angles during a gait cycle were measured and graphed for comparison with each limb joint among mammals with four typical foot postures. The kind of gait was determined in relation to the limb length ratio, the gait cycle and the position of the center of gravity. The joint angle of limbs is in relation to foot posture. The wrist joint in walking is analogous to the knee joint in the degree, direction and timing of flexion.

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