The influence of clinostat rotation on the fertilized amphibian egg

Unrestrained, fertilized eggs ofRana pipiens andXenopus laevis were rotated in a plane parallel to the normal gravity vector. InR. pipiens rotation at 1/4 rpm for 5 days at 18°C produced a significantly increased number of commonly occurring abnormalities. Rotation at 1/15, 1/8, 1, 2, 5 and 10 rpm did not significantly affect normal development.X. laevis eggs reacted similarly.R. pipiens eggs were most sensitive to rotation at 1/4 rpm when exposure was initiated before first cleavage. Mixing of intracellular constituents apparently occurred only at 1/4 rpm inR. pipiens (of the clinostat speeds studied), and may have been the cause of the increased abnormality observed at this rate.