I Substantial aspects of succession. It is bilateral relation between feudal service and fief that distinguishes the family of Samurai from others. (1) As to service, we find an official post which corresponded to the rank of family, and a successor was placed in a little lower rank than his father's, and took up a lower post. (2) As to the right of daimyos vassals, they could not rule over their own fief even in the earliest period, but could only collect land-tax. But its direct collection system was also denied in middle period, and after that rice provision system came to be adopted. Their real income, of which the standard persentage was 40 per 100 koku (_??_), was 12-25 per 100 a year, and the rest was cut down according to the clan's financial policy. II Quantitative aspect of succession. In this clan, Serokusei (_??__??__??_), hereditary system which guaranteed inheritance of father's whole fief was carried out in Kan-ei (_??__??_) 10 (1633) and continued till Horeki (_??__??_) 6 (1756). After this year it was changed into Segensei(_??__??__??_), diminishing hereditary system which cut down some portions for relief of finance. But on the other hand, we cannot overlook that legal security was increased by legislation against insecurity through daimyo's arbitrariness and foot-soldiers ( Kachi _??__??_) succession was newly permitted. III Succcessor and forms of succession. (1) On primogeniture : It was established in the Genroku (_??__??_) -Kyoho (_??__??_) ages (1687-1734) because of the following : (i) the expectability of fief-increase disappeared because land reclamation work was faced with limit, (ii) division of fief meant degradation of government post owing to gradation by quantity of fief, (iii) in the same ages the authority of the eldest son was established.(2) On adoption : Its purpose was defined on succession. Its necessity was absolute to vassals, but to daimyo was not so much, and so in early period it was prohibited as one of the vassal control policies. In accordance with command of Tokugawa central government ( Bakuhu _??__??_), in every clan, we find there. were some principles such as (i) adoption must be made among the same rank, (ii) the priority of the same surname and the eldest line, (iii) the exclusion of woman's line.