Frequency of divorce varies from society to society according to their evaluation of marital union. Some anthropologists such as Gluckman (1950), Leach (1957), Fallers (1957), Ackerman (1963) attributed the problems of marital stability to kin-group politics. It seems that they presuppose social structure or grouping as a determinant of the value of marriage. The limit of these theories becomes manifest when some other value system is introduced from outside world. This is the case appeared in Malay villages. In this paper the author tries to show such an example through comparison of Malay divorces in three villages. Interpretation of Islamic ideas on marriage and divorce varies from place to place causing different divorce rates : the traditional interpretation is related with frequent divorces while the modern interpretation with a decrease in spite of unchanged function of kinship structure. This type of wide variation in divorce occurrence, either spacial or historical, may be found among the people whose kinship structure facilitate divorces.

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 In this paper empirical description and analysis of the rice market and the rice policy of South Vietnam in the sixties and early seventies up to August 1974 were done. The emphasis is placed on rice marketing and related policies, and on investigation of the reliability of statistical data concerning rice.
 The rice economy in South Vietnam was affected greatly by scope and intensity of war. From 1965 the country had to import rice by considerable amounts every year changing its position from the traditional rice exporter to a large importer. But from around 1969 total rice production increased rather rapidly. The area planted to the HYV of rice also expanded rapidly. This together with the fast execution of the Land-to-the-Tiller Program from 1970 seemed to contribute the fast increase of rice production and yield in the early seventies.
 Rice marketing was virtually controlled by the overseas Chinese, and it seemed quite efficient although there might be some monopolistic control of the marketing. Capacities of rice mills and warehouses were enough though they need considerable repairs and improvements. Need of cheap dryers was very high because of the recent fast expansion of the HYV which was harvested in rainy season. Lack of dryer deteriorated the quality of rice and decreased its price.
 The rice marketing policy through the National Food Administration since 1973 was successful to a considerable extent as far as its effects on rice price were concerned. It was made possible by the availability of the large amount of rice imported by the PL480 food aid program from the United States and by the legal, administrative, and military measures of the government. The government's fertilizer price policy was also successful supported by import of fertilizer from the United States on aid basis, and contributed considerably to the fast expansion of the HYV of rice. Concerning the rice statistics, planted area and production were underestimated by about 10-20% during the sixties, but this divergence seemed to decrease in recent years. The production statistics did not included rice production from the area under solid NLF Control. Foreign trade statistics were most reliable, and the domestic shipment statistics least. Per capita rice consumption for 1972 was estimated as a balance from these statistics, but because of the error in the shipment data and of the underestimated population, the estimate was too high and biased too much regionally.

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 Correlation coefficients between all pairs of 29 variables that had been described previously in relation to fertility and material characteristics were computed for the same 410 tropical Asian paddy soil samples.
 Chemical characters related to base status are highly correlated not only with each other but also with such character groups as textural composition, clay mineralogy, and total chemical composition.
 Characters related to organic matter status are not highly correlated with any of the other character groups, though their mutual correlations are high. The same holds for characters related to phosphorus status.
 Multiple regression of CEC on the contents of different clay mineral species and organic matter was studied. The 14 Å minerals alone explained more than 80% of the variance of CEC. The 7 Å and 10 Å minerals also contributed significantly, but the contribution of organic matter to CEC turned out to be insignificant.
 Hayashi's theory of quantification (No. 1) was adopted to assess the contributions of such qualitative variables as climate, relief, and texture to organic matter status of the soil. Climate was proved to be most relevant to the reserve of mineralizable nitrogen, while local relief contributed most to TC and TN. Effect of texture on accumulation of organic matter was clearer under a drier climatic condition.

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 The Vietnamese part of the Mekong Delta is divided into seven physiographic divisions in relation to rice culture. They are Trans-Bassac Horst, Floodplain, Modern Delta, Coastal Complex, Broad Depression, Plain of Reeds and Western Coastal Zone. Some of them are further subdivided. Floodplain is a graben filled up by the Mekong and the Bassac's fluviation. Trans-Bassac Horst is a slightly uplifted geologic block with flat ground surface. Modern Delta is the downward extension of Floodplain and it has deltaic networks of rivers of great tidal range. Broad Depression is a blocked-in swamp behind Coastal Comples. These five divisions form the important rice growing area of the delta. The last two, Plain of Reeds and Western Coastal Zone, are swampy areas on the margin of the delta still waiting possible reclamation. The demarcation of the divisions and their subdivisions are given in Fig. 2.
 The delta is a wet terrain, being signified by the plentiful monsoonal rainfall with even distribution over the rainy months (Fig. 3), and by low-lying topography. The delta is, however, divided into two parts with respect to the hydrologic conditions, in which the alternation of dry and wet cycles are more pronounced in one region, and less significant in the other. The two classes are closely related to the physiographic divisions; Trans-Bassac Horst, Floodplain, and Coastal Flat comprise the former region, and Modern Delta, Broad Depression and Lagoonal Swale belong to the latter.
 An adaptation of the rice growing methods to the given hydrologic conditions is the character that defines the rice culture of the delta. Rice growing does not rely on river water, if not at all, but it depends more on rainfall and its localized run-off which is controlled by micro-relief. The above characteristics of the present hydrology are summarized in Table 1 corresponding to the physiography and typical types of rice culture.
 The river water, however, will have to be tapped to meet the requirement of water for TN rice (new high-yielding varieties of rice) which is rapidly extending its area as the early rainy season's crop as well as the dry season's crop. Abundant flow of rivers, creeks and canals is readily usable as it is often perennial being induced by the significant tidal fluctuation in the sea and in major rivers. The possible types of river water control and utilization are described and summarized in the same table, in view of giving the favorable conditions to the extended TN rice and possible diversification of the delta agriculture.
 The natural environment is one which will allow further modification by the efforts of individual farmers and of local communities once infrastructual and institutional facilities are provided by the Government.

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 For the agricultural development of the Mekong delta, two groups of soils pose difficult problems, one being acid sulfate soils that extend over a million hectare and the other being coastal saline soils along the coast line having 1.2 million hectare extension.
 Acid sulfate soils occur extensively in the Plain of Reeds along the Cambodian border and in the Ha-Tien Plain. A more scattered occurrence is also seen in the Trans Bassac lowlands.
 They are formed on brackish water sediments in the broad depressions which are located far away from the main river courses. In addition, swampy conditions under which they occur hinder the access of any reclamation means.
  Strong soil acidity resulting from oxidation of the accumulated sulfides in the sediments can be mollified either by heavy liming or by washing with a large amount of fresh water. Both require quite a heavy investment. In case of the Mekong delta, however, the Ha Tien area produces limestones, which are now being quarried for cement industry. Making the best use of this local resource for the reclamation of acid sulfate soils should merit serious consideration.
 Coastal saline soils may be classified as saline alkali soils according to Buringh's criteria. They are neutral to slightly acid in reaction, but sufficiently high in free salts and high in exchangeable sodium percentage.
 The salinity is caused by a salt water intrusion during the low flow period of the Mekong river, i. e., during the dry season. The high tidal range (～3m along the South China Sea coast) is a factor that enhances the salt intrusion in the Mekong delta.
 Engineering measures such as construction of embankments, dike and channel plugs, and flap-gated culverts, are necessary to prevent the salt intrusion. Where salinity is not very serious, adjusting the rice growing stages to the water salinity condition, such that transplanting of rice seedlings is done during the low salinity period, lessens the adverse effects.
 As the irrigation water intake in the upstream areas during the low flow period could enhance the salt water intrusion in the lower reaches, care should be taken in planning the irrigation schemes for the dry season crops.

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 Firstly, the basic characteristics of the lowland rice agriculture were reviewed in comparison with those of the upland crop agriculture. They are summarized as below.
[table]
 Secondly, the Mekong Delta were divided into three broad regions according to the relevant physical conditions. The differences among the regions in the traditional rice culture as well as in more recent trends of changes were explained by the differences in their physical conditions.
 Thirdly, the implications to a development project of the basic characteristics of the rice culture in general and those of the Mekong Delta in particular thus assessed were discussed. The following points were mentioned.
(1) Any development project must take into account the gradual but steady amelioration of the land and water conditions by the peasants' own initiative. It is not realistic to assume that the traditional rice culture is a static one and could drastically be developed into a bright modern agriculture only by a large scale engineering project.
(2) Different varieties of rice are chosen by the peasants according to the degree of uncontrolability of the water condition. In the varietal improvement as well as in the amelioration of the land and water conditions, there will be no once-and-for-all development.
(3) A comparative study on the human manipulation of the hydrographic conditions on the rice land under the different environmental settings will provide the sound bases for formulating a development project.
(4) A particular attention should be paid to the lowland without the distinct desiccation of the land throughout the year, for this type of land has been developed to any significant extent in no other part of the world than the Mekong Delta.

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 The first part of the study is concerned with actual farmers' economic situation based on farm household economy survey data in delta region in 1972-73. It shows relatively heavy weights of expenditures (including costs of farming and non-farming businesses, and costs of living) in gross revenue (Table 5). Thus it seems to be rather difficult for individual farmers to save money for buying new equipments and machines. By divided net farm revenue (or income) per ha into two parts as labor efficiency (net farm revenue per labor force) and capacity of labor forces to land (labor forces per ha), the data of sample provinces in the Delta (Dinh Tuong, Vinh Long, and An Giang) result in different pattern of distribution combining net farm revenue to efficiency and capacity factors (Figures 6 and 7).
  Surveys of rice production cost indicate differences in cost structure and profitabilities of rice production for high-yielding varieties and local varieties including traditional floating rice. For the high-yielding varieties, fairly intensive labor requirements and increased demands for other input like fertilizers and chemicals are considered as important.
 The last part of the study deals with several problems which farmers face on farming. Among problems which farmers pointed out, water control in the wet season and irrigation in the dry season are serious problems. Price increasing tendency of fertilizers and chemicals (insecticides, pesticides, weedicides, etc.) are another crucial problems. Besides, the study describes other kinds of necessary information for farming and sources of information when farmers want to get them.

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 Based on the author's collection and the literature cited, 176 fish species are recorded from inland waters of the Vietnamese Mekong delta (Table 1). The ichthyological fauna of the area is characterized, in comparison with that of the Laotian Mekong, by less abundant cypriniform fishes and more numerous clupeiform and perciform species (Table 2). The mainstream waters in the delta may be divided into three sections according to faunal features, as illustrated in Fig. 1. Excepting Cirrhinus jullieni and Thynnichthys thynnoides, long-distant migratory forms found in the Cambodian and Laotian Mekong do not descend deep into the Vietnamese delta. Pangasianodon gigas, in particular, does not enter delta waters. As in other part of the lower Mekong basin, a great many species perform seasonal movement in delta waters in accordance with seasonal change in water conditions, dispersing in flooded areas during wet season and returning to rivers during dry season.
 Fishery productions in the delta are shown in Tables 3 and 4,together with those in neighboring areas. The delta produces 80～90% of total freshwater fish production in South Vietnam. Important food fish are enumerated in Table 5.
 Freshwater fishes cultured in the delta are Puntius altus, P. gonionotus, Leptobarbus hoeveni, Cyprinus carpio, Pangasius micronemus, Clarias macrocephalus, Channa striata, C. micropeltes, and Tilapia mossambica. The source of fingerling for culture is natural spawning, except for the ca chep (C. carpio) and ca phi (T. mossambica). The commonest fishculture practices are the pond culture of the ca tra (P. micronemus) and the floating cage culture of the ca he (P. altus), ca loc (C. striata) and ca bong (C. micropeltes).
  Introduction of large-scale freshwater fisheries does not seem suitable to the delta in view of the limited productivity of the limited area of water. Aquaculture is an effective and advantageous means of utilizing land and water resources of the area. Extensive mono- and polyculture of plankton feeding and herbivorous species with pond fertilization seems most advantageous in the future. Fishculture combined with livestock, using manure from the livestock for natural fertilization of ponds, will be highly suitable to the conditions of the delta.
 Future changes in hydrological conditions of the delta will be various according to the nature of reformation work in the upstream areas as well as the delta. In any cases, marshy, low-lying lands, either existing or newly formed, should be retained in order to keep providing many sorts of fishes with their spawning and growing grounds.

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 In this paper, investigations and plans through coordination made by the Mekong Committee, as a blueprint for the future development of the lower Mekong basin, are presented based on selected reports and documents in the Secretariat of the Committee, ESCAP. The topics discussed in this part are : demographic state, arable land, food production, GNP, carrying capacity of the basin, hydrometeorological and engineering survey, socio-economic study, financial resources for pre-investment investigation and construction of projects, Pa Mong Project scheme and its downstream effects, pioneer agricultural projects, and other projects in the delta. Taking above items together the conclusion is that the potential of land productivity and the human resource of the Mekong Delta is probably the highest among other areas in the lower Mekong basin. However, there would be various ways and means to be chosen to raise the agricultural production, according to soil and hydrological conditions in the Mekong Delta. A way adaptable to a particular region of the delta may not be to the other, and strategies usually involve low investment approach which farmers can handle it, and high investment approach like flood control which even international cooperation is needed.

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