Chromosomes and Genes: The Biological Basis of Heredity. By P. C. Koller, MD. Price, $1.95. Pp 144. Oliver and Boyd, Edinburgh, American distributor W. A. Benjamin, 2 Park Ave, New York 10016, 1968. I obtained these two books during a recent visit in London. They share some common features: both deal with basic problems of cell-biology; both are excellently written; they are inexpensive. However, in presentation they are quite dissimilar, being directed toward different strata of readers. Harris' book was written for advanced students about a wellcircumscribed subject: the interrelationship of nucleus and cytoplasm. It is an outgrowth of a series of lectures he gave at Oxford. The book contains six chapters: (1) "The Expression of Genetic Information"; (2) "The Genetic Operator Model"; (3) "The Search for a Messenger"; (4) "Regulation"; (5) "Hybrid Cells"; and (6) "Differentiation." The topics are discussed in full detail; corresponding references are marked in the