The Panel on Gravity of the Space Science Board ([ref.67]) stated that the major effects of low gravity would be expected in heterocellular organisms that develop in more or less fixed orientation with respect to terrestrial gravity and which respond to changes in orientation with relatively long induction periods, including the higher plants. On the other extreme are the complex primates which respond rapidly, but whose multiplicity of organs and correlative mechanisms make the occurrence of malfunction and disorganization probable, but not certain. The Panel recommended emphasis on early embryogenesis and histogenesis, particularly of plants during exposure to low gravity, and anatomical studies after low gravity. They stated that perturbations of the environment to which the experimental organism is exposed must be limited or controlled to reduce uncertainties in interpretation of results. At the same time, the introduction of known perturbations may assist in isolating the effects due solely to gravity. Ground-based clinostats and centrifuges should be used in conjunction with the experiments, and an attempt should be made to extrapolate effects of low gravity with the clinostat. The study of the effects of unique or unknown space environmental factors will probably yield unexpected results which may drastically modify future technical approaches. The results from these biosatellite studies will have broad application to longer term, manned space flight, including manned space stations and lunar and planetary exploration. The biosatellite program is a second-generation series of carefully planned and selected experiments, including some highly sophisticated experiments which have required several years of baseline study and equipment development. These orbiting recoverable biosatellites will provide opportunities for critical testing of major biological hypotheses in the areas of genetics, evolution, and physiology. The scientific community showed great interest in the biosatellite program, and scientists from universities, industry, and Government have submitted 185 flight experiments involving primates and other mammals, vertebrate and invertebrate animals, micro-organisms, and plants. The selected biosatellite experiments include studies at the cellular, tissue, and organism levels, including embryological development and growth experiments at the tissue level and physiological, behavioral, reproductive, and genetic studies at the organism level. The experiments are divided into six categories: (1) Primates (2) Mammals (nonprimate) (3) Animal, cellular, and egg (4) Plant morphogenesis, photosynthesis, and growth (5) Biorhythm (6) Radiation