Time relationships in the cleavage of the normal fertilized egg of Arbacia punctulata.

Quantitative data are presented indicating the extent of variability in the time of cleavage of normal fertilized eggs of Arbacia punctulata. It is a pleasure to acknowledge the valuable suggestions and criticisms of Professor Arthur K. Parpart during the course of the experiments described in this and the preceding paper, and those of Professor Douglas A. Marsland and Professor M. J. Kopac at the final manuscript stage.