A "Normal" Development of Denuded Eggs of the Starfish, Asterina Pectinifera*

Experimental conditions that allow "normal" development of starfish eggs stripped of the fertilization membrane are reported in this paper. Four kinds of intercellular relation are distinguished during the pre-hatching stages of these eggs. Cells from 2- to 8-cell stages are hardly related to each other, while those from 16- to 128-cell stages are bound loosely together. After the 8th division (about 5.5 hr after insemination at 21°C) cells adhere closely and cooperate with each other to perform morphogenetic movement of "blastulation". This relation is taken over by that of a true multicellular system at about 10 hr after insemination. Closely after this, the function of cilia carries the embryo away from the substratum.