V. B. WIGGLESWORTH and J. A. RAMSAY

For the CONTENTS at the beginning of the article by G. G. Selman and C. H. Waddington on page 700, substitute

For the legend to Fig. 3 on page 739 of the article by J. M. Mitchison and M. M. Swann substitute

Fig. 3. Stiffness changes at fertilization. Four eggs of Psammechinus miliaris;, A, stiffness of normal fertilized eggs at sperm aster stage ; B, stiffness of normal unfertilized eggs ; C, stiffness of unfertilized eggs treated with trypsin. Corrected stiffness is in dynes/cm. 2/μ deformation for 100/μ diameter egg and 50/μ diameter pipette.

For equation (xxvi) on page 809 of the article by J. Gray and G. J. Hancock substitute

or