THE ECOLOGICAL SURVEY on which this book is based began to be planned in 1942, and since 1945 has been mainly centred upon Oxford University's estate at Wytham Woods, where a rich series of habitats from open ground and limestone to woodland with many springs and marshes interspersed occupies a hill set in riverine surroundings. Here biological research workers from the University have accumulated a considerable body of knowledge, some of which I have arranged in a general setting that allows one to comprehend some of the inter-related parts of the whole system. It is also intended to provide...

n this book I have tried to bring together ideas from three different Istreams of thought with which I have been closely concerned during the last thirty years or so. The first is faunal history, usually regarded as a purely academic subject, but to some of whose events can be traced a number of the serious dislocations taking place in the world today. The second is ecology, particularly the structure and dynamics of populations. The third is conservation. I first published a few ideas about the signifi- cance of invasions in 1943, in a war-time review called Polish Science and Learning,...