When you consider that it once took such wild unlikelihoods as a pig-headed sheep to evoke an explanation of biological inheritance, you begin to see the potential fascination of the subject. Jacob, who shared the 1965 Nobel Prize for medicine with Jacques Monod, fulfills that potential on a grand scale, combining something of the popular liveliness of a book like Rats, Lice and History with the serious thematic and contextual approach that earmarks the best recent intellectual history -- for that really is what he is writing. The evolution of the 16th century concept of ""generation"" into our present molecular understanding of heredity is taken as a demonstration of the processes of thought as a cultural and historical phenomenon, which will be accelerated along some lines and inhibited in others according to the devices available at any given time. Thus, instead of isolating ancestral ideas, Jacob concentrates on the acquisition, over four centuries, of a suitable intellectual apparatus (mechanical apparatus is relegated to the background) -- classification, methods of analysis and experimentation, and, most especially, potentiating theories, which were shared among all the sciences and responsive to suggestions from society at large, 19th-century horticulture and statistical physics, for example, proving more important in the long run than, say, Lamark and his premonitory ilk. The main theoretical tributaries, and their inherent obstacles, are discussed in more or less chronological lectures, which are perhaps the most exquisite application to date of Kuhn's paradigm of scientific revolutions. This is not for beginners, but near-beginners and sophisticates both will propel themselves through provided they have any interest at all in culture, history or science, and not necessarily in genetics. Notes.