DURING the greater part of his life, man changes but little in form. In this important character he differs greatly from the majority of living organisms. By reference to ourselves, the concept of the form of an organism appears well defined, but this is to a large extent the result of our own constancy. In most organisms, our task is not that of describing a single well-defined structure, but the description of a sequence of continuously changing structures. Problems of Relative Growth. By Julian S. Huxley. Pp. xix + 276. (London: Methuen and Co., Ltd., 1932.) 12s. 6d. net.