WRINKLED BLASTULA OF THE SEA-STAR, ASTERINA MINOR HAYASHI

In naturally raised embryos of Asterina minor, the changes of internal structure during the wrinkled blastula stage were followed. Eight hours after spawning, blastomeres on the surface of the coeloblastula drop into the blastocoel and eventually form multiple invaginations of the blastodermal layer. Four and a half hours after the commencement of wrinkling, the blastocoel appears to be filled by the developed invaginations. The invaginations then decrease in number and complexity, and 11.5 hr thereafter the wrinkled blastula stage ends, although gastrulation takes place before the complete disappearance of the wrinkle-invaginations.