With 'Biogeography and Ecology in South America' as the general theme, a total of twenty-nine contributions by thirty authors is offered here in two volumes, being volumes 18 and 19 of the Monographiae Biologicae. Most of these discussions deal with decidedly specialist themes and the editors have been particularly concerned to ensure that the authors enjoyed the greatest possible freedom in the preparation of their work in order that different points of view and interpretations, together with some questions of controversy, may be clarified. This also applies, of course, to the several...