According to Spencer, the "obtaining of wives by services rendered, instead of by property paid," is a "cause of improvement in the treatment of women," and constitutes therefore a "higher form of marriage," developing "along with the industrial type" of society. "Obviously, a wife long labored for is likely to be more valued than one stolen or bought;" and the long association of the lovers during the time of service is likely to foster more refined sentiments than the "merely instinctive;" to imitate "something approaching to the courtship and engagement of civilized peoples."[590] But, on the other hand, without denying that these results may follow, Westermarck forcibly objects that "industrial work promotes accumulation of property, and consequently makes it easier for the man to acquire his wife by real purchase." Serving for wives is prevalent among such rude races as the Bushmans and Fuegians. Hence it seems "almost probable that marriage by services is a more archaic form than marriage by purchase; but generally they occur simultaneously."[591] [590] SPENCER, _Principles of Sociology_, I, 754, 755. On the modification of the servitude of the wife through the service-contract see LETOURNEAU, _L'évolution du mariage_, 137; BANCROFT, _Native Races_, I, 134 (Kenai). [591] WESTERMARCK, _op. cit._, 391, 392. By far the most common way of purchasing a wife is by giving property in exchange.[592] Usually the amount of the price is arranged, like any other bargain, by agreement between the interested parties; but sometimes it is established by custom.[593] Always where the contract is merely a commercial transaction the price is in theory an equivalent for the economic loss sustained by the family or _gens_ of the bride.[594] But the amount varies in every possible way. Often it depends upon the rank or beauty of the woman; or it may be determined by her strength and capacity for bearing children. It varies also with the economic condition of the times, the wife-market depending largely upon the law of supply and demand. In hard times, or where there is an excess of women, wives are cheap; when times are good or women scarce, the price rises in proportion. Among peoples somewhat advanced in culture sentiment must, of course, be taken into account. Where it is regarded as a disgrace to accept a small compensation for a daughter, high prices may lead to celibacy. Such, at the beginning of the past century, was the case in Servia, where the bridegroom, in addition to the purchase price, was expected to bestow liberal presents, not only upon the bride and her mother, but also upon all her near relatives. The presents were so expensive that many a "poor fellow was unable to marry at all;" and so Black George in 1849 had a sumptuary law enacted restricting the price of a girl to one ducat, and this must be paid before the wedding.[595] But the bride-price "varies most according to the circumstances of the parties, and according to the