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3.1.2. When does a merger become a galaxy?

The observed evolution in the merger rate, coupled with the expectation from theory that of mergers move galaxies up and down the Hubble sequence (cf. the lectures given by Prof. White in this volume), forces morphologists studying the high-redshift Universe to confront both philosophical and practical issues that seemed rather semantic and trivial at low redshifts. For example: when should an amorphous blob of components be regarded as single morphologically peculiar galaxy, as opposed to a system of interacting proto-galaxies? de~Vaucouleurs used to dismiss the notion of considering mergers to be fundamental morphological units with the observation that ``car wrecks are not cars''. But when the road is littered with wrecks, and when the by-product of a wreck is another working car, it may be time to re-assess the wisdom of restricting morphological classification to regular-looking systems. Classification schemes which explicitly incorporate measures of asymmetry and bimodality are needed to realistically capture the appearance of galaxies in the high-redshift Universe.