Cell migration during the reassembly of dissociated embryonic cells of sea urchins

Disaggregated single cells from the embryos of Strongylocentrotus purpuratus were allowed to reaggregate and reform quasi-normal embryos in culture. In this investigation, emphasis was placed on cell migration and its role during cell segregation. Epithelial cell migration appears to be initiated through the sequential formation of (a) cytoplasmic blebs, (b) microvilli, (c) filopodia and (d) hyaloplasmic lamellae. After functioning as a locomotive structure during cell migration, the lamella enlarges and forms a hyaloplasmic sheet, which makes up part of the blastocoel wall. The blastocoel wall is the first recognizable structure reformed in the reassembling embryo.