Abstract
Possible influences of the gravity on the early development of frog eggs were reviewed. Influences of the gravity can be analyzed by gravity-perturbation experiments, such as rotation or inversion, simulated weightlessness (clinostated), and centrifugation (hypergravity) experiments. Completely inverted eggs failed to develop the normal dorsal-ventral polarity and resulted in permanent blastulae. Incompletely inverted or rotated eggs developed to "norma1" tadpoles, while the number of the primordial germ cells was greatly reduced. Centrifugation of the fertilized eggs caused a modification of the future dorsal-ventral polarity, and in some cases caused twinning (double embryo formation). The biological significance of the gravity during the early development of frog eggs were discussed.
