is also notable for its use in the first widely used method of pregnancy testing. In the 1930s, two South African researchers, Hillel Shapiro and Harry Zwarenstein, students of Lancelot Hogben at the University of Cape Town, discovered that the urine from pregnant women would induce oocyte production in X. laevis within 8–12 hours of injection. This was used as a simple and reliable test up through to the 1960s. In the late 1940s, Carlos Galli Mainini found in separate studies that male specimens of Xenopus and Bufo could be used to indicate pregnancy Today, commercially available hCG is injected into Xenopus males and females to induce mating behavior and to breed these frogs in captivity at any time of the year. Xenopus has long been an important tool for in vivo studies in molecular, cell, and developmental biology of vertebrate animals. However, the wide breadth of Xenopus research stems from the additional fact that cell-free extracts made from Xenopus are a premier in vitro system for studies of fundamental aspects of cell and molecular biology. Thus, Xenopus is the only vertebrate model system that allows for high-throughput in vivo analyses of gene function and high-throughput biochemistry. Xenopus oocytes are a leading system in their own right for studies of various systems, including ion transport and channel physiology. Xanthos et al 2001 uses oocytes to uncover T-box expression earlier than previously found in vertebrates. Although X. laevis does not have the short generation time and genetic simplicity generally desired in genetic model organisms, it is an important model organism in developmental biology, cell biology, toxicology and neurobiology. X. laevis takes 1 to 2 years to reach sexual maturity and, like most of its genus, it is tetraploid. It does have a large and easily manipulated embryo, however. The ease of manipulation in amphibian embryos has given them an important place in historical and modern developmental biology. A related species, Xenopus tropicalis, is now being promoted as a more viable model for genetics. Roger Wolcott Sperry used X. laevis for his famous experiments describing the development of the visual system. These experiments led to the formulation of the chemoaffinity hypothesis. Xenopus oocytes provide an important expression system for molecular biology. By injecting DNA or mRNA into the oocyte or developing embryo, scientists can study the protein products in a controlled system. This allows rapid functional expression of manipulated DNAs (or mRNA).