‘Growth’ is a word of notorious imprecision, but it stoutly defies semantical reform. It may mean increase of length, area, weight or volume; it may mean the act or accomplished fact of reproduction, i.e. increase of number; or it may simply mean development—the adverb is not well chosen—with all that development implies of increasing complexity and elaboration. I shall restrict growth here to its simplest meaning, change of size, but I shall consider also the changes of shape which are the outcome of inequalities in the rate of change of size.