Provides a reference work, in particular the key to the identification of the southern African species. This book has a chapter on Bilharzia and its snail hosts, especially important at a time when Primary health care programmes are implemented. It also addresses access to safe drinking water to be regarded as a fundamental human right.

The first half of this book is primarily a systematic survey of the snails, beginning with glossaries, keys for identification to genera and a checklist of species. This is followed by a synopsis of species, with brief notes on ecology, distribution and parasites. Relationships are then described between snails and schistosomes and with other parasites. The book goes on to consider the factors affecting snail populations and possible methods for population control.

CD ROM to accompany this book available from Library Office.

All aspects of the ecology of freshwater molluscs are discussed in this unique volume. Extensively referenced and providing a synthesis of work from the nineteenth century onwards, this book will appeal to professional ecologists, evolutionary biologists and parasitologists interested in these diverse invertebrates.

Southern Africa is certainly not a naturally bounded area so that there are several possibilities for delineating it and concepts about its extent. Wellington* discussed the various possibilities for delineation and suggested that one line stands out more clearly and definitely as a physical boundary than any other, namely the South Equatorial Divide, the watershed between the ZaIre, Cuanza and Rufiji Rivers on the one hand and the Z ambezi, Cunene and Rovuma Rivers on the other. This South Equatorial Divide is indeed a major line of separation for some organisms and is also applicable in a certain geographical sense, though it does not possess the slightest significance for many other groups of organisms, ecosystems or geographical and physical features of Africa. The placing of the northern boundary of southern Africa differs in fact strongly per scientific dis cipline and is also influenced by practical considerations regarding the possibilities of scientific work as subordinate to certain political realities and historically grown traditions. This is illustrated, for example, in such works as the Flora of Southern Africa, where the northern boundary of the area is conceived as the northern and eastern political boundaries of South West Africa, South Africa and Swaziland. Botswana, traditionally included in the area covered by the Flora Zambesiaca, thus forms a large wedge in 'Southern Africa'.