Alfred Marshall is often quoted for his statement that "the Mecca of the economist lies in economic biology" and he is seen as a father of evolutionary economics. However, the limited character of his evolutionary theory, and its close resemblance to t he ideas of Herbert Spencer, are sometimes misunderstood or ignored. Th e argument in this paper is that Marshall saw the value of the biologi cal metaphor for economics but in part the Spencerian influence thwarted the development of an adequate evolutionary analysis. Copyright 1993 by Royal Economic Society.