This study is based on a sample of about 100 languages with numeral classifiers. An attempt is made at reconstructing the dynamics of the process by which such systems arise, develop, and decay. Among the hypotheses advanced are the following: (1) numeral classifiers involve the overt expression of one kind of quantification, namely, counting by units; (2) the numeral classifier construction is modelled after the measure construction with mass nouns and hence arises in languages with previous mass-count noun distinction; and (3) the classifier in a numeral classifier language has the same function as a singulative does in a language with a collective-singulative distinction. (Author)