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The existence of perceptual completion is well documented by a wealth of psychophysical studies, perhaps only rivaled by the many different interpretations of the underlying mechanisms. This chapter argues that some forms of completion are likely implemented early in the visual system. It reviews experimental data showing completion-like properties across the blind spot representation in the striate cortex of monkeys. This property seems to be based on interpolation of spatially collinear stimuli. Experimental evidence is presented for interpolation not restricted to natural scotomata like the blind spot. Additionally, the chapter presents findings of spatial interpolation from striate cortex cells of the opossum, a more primitive mammal.

This chapter synthesizes what we have learned about the weasel and explores greater detail her connection to the world of women and childbirth. It examines the legend of the weasel's oral birth and its extraordinary agility; the particular physical characteristics and behaviors of the weasel that make it especially suitable as a symbolic expression for pregnancy and childbirth; and analogies between the weasel and the opossum and their links to the world of birth.

This chapter describes the taxonomy of Lophogastrida and Mysida, small shrimp-like crustaceans commonly known as ‘opossum shrimps’ because of the ventral brood pouch in the female. Because of their highly adaptive nature, they have progressively invaded new areas via new connections of water systems and through ballast water. The chapter covers their life cycle, ecology, and general morphology. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.

Costa Rica is one of the most biotically diverse countries on earth, with 4% of known terrestrial plant and animal species in only 0.04% of the world’s land surface. The country’s mammal fauna is equally diverse, with more than 207 species (4.8% of the world’s 4629 species) in an area of 51,022 km2. The majority of the world’s mammal species and Monteverde’s fauna are small (< 0.5 kg), nocturnal, and secretive. We know considerably less about most neotropical mammals and other vertebrates than we do about birds, which are more easily observed and communicate with sounds audible to humans. Although certain species of mammals have been studied in Costa Rica (Janzen 1983a, Timm 1994, Vaughan and Rodríguez 1994), and Monteverde is one of the best-known regions of the country biologically, there has been little work on the ecology, distribution, abundance, altitudinal zonation, systematic relationships, and biogeography of most mammals. Deforestation and other human disturbances have had a significant impact on the native mammals of the region; knowledge of Monteverde’s mammals is vital to understand how habitat changes affect tropical montane mammals. In this chapter, we provide an overview of the mammal fauna of the Monteverde area. We discuss the biology and abundance of some of the area’s species, document how these are changing, and explore conservation issues. Most of the research on mammals at Monteverde has centered on bats or rodents, the two most diverse groups. Much of our knowledge of other species consists of isolated observations. We augment published reports with unpublished observations made by ourselves and colleagues. We also examined most of the Monteverde mammal specimens in museum collections to verify species identifications and to understand better their systematics, ecology, and distribution. We integrate this information into a list of the mammals that occur in the region, document their occurrence in each life zone, and estimate their overall abundance.