The body weight, external and cranial characters of Japanese hares (Lepus brachyurus brachyurus) killed at various growth stages were measured in order to elucidate their growth and development and to obtain criteria for age determination. Almost all the characters showed a rapid growth in the early stage and attained adult values before ca. 1-year-old, meaning the shortening of the juvenile and subadult stages by acceleration of the growth rate. Such acceleration is thought to heighten the survival value of young and to be advantageous to minimize the energy investment for rearing infants by the mother. It is possible to determine the age by basically using the eye lens weight during 1 year after birth. In addition to this criterion, the eruption, replacement and attrition of the incisors and cheek teeth, and the presence or absence of the distinguishable os interparietale are good criteria within 1 month after birth, and the degree of ossification of the sutura sagittalis is of use from 1 till 3 months. During 3 months after birth, the more accurate age determination is possible by corrections based on the size of the cranium, body weight and external characters.

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Development, sexual dimorphisms and individual differences of the skeleton of the striped dolphin (Stenella coeruleoalba) living off the Pacific coast of Japan were examined. As materials, 38 individuals were used. Cranial skeleton reach adult plateau at the age of 3. Earbone increases little after birth. Most of postcranial skeleton reach adult size at the age of 7-10. Length of thoracic and lumbar vertebrae, thylohyals, stylohyals, ribs and sternals continue to grow at the age of 15-19. Length of the 2nd-the 7th cervical vertebrae reach adult plateau at the age of 3. The front edge of the occipital in adult female overhangs the frontals to form a crest, but in adult males the crest is typically absent. Width of rostrum (except for at base) and length of basyhyal, the 2nd-8th ribs and pelvic bones are larger in male on average than in female. Individual differences are found in the number of vertebrae (77-81), chevron bones (26-31), phalanges of the 1st digit (3-4), the 2nd (5-8), the 3rd (7-10) and the 4th (2-3), teeth in upper left (43-52), upper right (43-52), lower left (41-50) and lower right (42-53) . The species reaches physical maturity at ages between 15 and 19.

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A total of 285 Japanese wild boars without viscera were weighed and measured for head and body length, shoulder height, and girth. The growth of females reached asymptotes at 3.5 years of age of 50 kg for body mass, 125 cm in head and body length, 70 cm in shoulder height and 95 cm in girth. On the other hand, growth of males did not reach asymptote at least up to 4.5 years of age of 95 kg for body mass, 145 cm in head and body length, 77 cm in shoulder height, and 118 cm in girth. Growth for males was expected to decline first in head and body length, next in shoulder height, third in girth, and finally in body mass. Growth of all measurements for females reached asymptotes at a similar age. Males exceeded females in all the measurements. Sexual differences increased linearly with advancing age from 0.5 to 4.5 years of age and became bigger in order of shoulder height, head and body length, girth, and body mass. Comparing with other two populations, sexual dimorphism of Chugoku population was the biggest.

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The structure of microhabitats used by Apodemus argenteus and A. speciosus, which are generally regarded as sympatric at the macrohabitat level, was analysed ; and habitat segregation patterns and interspecific competition between these two species were discussed. Transects of 50 Sherman live-traps set 10 m apart were laid in forests at four sites in northern Kyushu. After mark-and-release, variables reflecting the structure, diversity of vegetation and physical factors were examined in a quadrat of 10 m² and a circle with the radius of 10 m both of which were centered on the trapping point. A discriminant function analysis by the stepwise method resulted in 66.6-100% of correct discrimination of microhabitats for the two species both at each site and at the four sites en bloc, indicating that A. argenteus selected microhabitats with characteristics of climax forests, and that A. speciosus did those with features of secondary forests. A principal component analysis on five selected variables revealed that the macrohabitat segregation between these two species was flexible. The more the two species approached each other, the more A. argenteus selected the microhabitat with complex strata of vegetation cover. The flexible horizontal and vertical microhabitat segregations would play a role in decreasing competition between these two species.

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Japanese Vespertilio has been classified into V. superans occurring in Ozukue-jima Islet (OJI) in Fukuoka Prefecture and V. orientalis (type locality-Horobe, Iwate Prefecture), based on mainly the presence or absence of the penile Pseudobaculum regarded as a most important key character : the former does not have it, while the latter has (Wallin, 1969) . In this connection, since the age of V. superans specimens examined by him is of decided importance, the presumed age dating from 30 June was adopted in this study, because parturition occurs near that time in both populations. The present ontogenetic study on the penis of OJI's bats revealed that the Pseudobaculum begins to develop -3 months after birth and is completed at the age more than -7 months. Accordingly, it is a matter of course that Wallin's specimens from OJI aged only -1 month lack the Pseudobaculum in their penis, and that the type specimen of V. orientalis at least-11 months old bears it. Taking also no difference in other characters including karyotypes between both species into account, it is thus concluded that V. orientalis is synonymous with V. superans, and consequently that all the specimens of Japanese Vespertilio should be called V. superans.

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Museum specimens of 210 red-backed voles from USSR, northeast China (Manchuria), and Korea were compared with 70 specimens of Clethrionomys rufocanus from Finland. Condylobasal length (CBL) correlated positively with ages determined by developmental stages of molar roots in the samples from Finland throughout the year. All skulls measuring CBL = 26 mm or more had roots in the samples collected from Finland in the first half of the year. In the Asiatic specimens collected in the first half of a year and from 41°N latitude and north (northern voles), all skulls with 26 mm CBL or more lacked alveolar capsules, indicating the development of roots. On the other hand, in museum specimens collected in the first half of the year and from 41°N latitude and south (southern voles), all skulls, even in skulls with 26 mm CBL or more, had strongly bulged alveolar capsules, indicating rootless molars. The occlusal patterns of M3 change with increase in CBL were the same between C. rufocanus from Finland and northern voles: simplex form was common in larger individuals, whereas the complex form was rare. On the other hand, the complex form was abundant in all CBL classes in southern voles. Northern voles were slightly narrower in interorbital width and slightly shorter in tail length than southern ones. I identified the northern vole as C. rufocanus, and the southern vole as Eothenomys regulus. I suggest that the true geographical demarcation line between the two species lies on the western and southern boundary of the Kaima Plateau, North Korea.

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