Multiple choice Cavitation begins to occur at which of the following stages of embryogenesis? 8-celled 16-celled 32-celled 64-celled 150-celled Reveal answer Fill a bubble to check yourself C Correct answer Explanation After compactation, the embryo is in the morula stage (32 cells). Cavitation occurs next in which the outermost layer of cells secrete fluid into the morula.