The relationship between the edge of the chick blastoderm and the vitelline membrane.

1. The edge of the chick blastoderm has been filmed as it migrated over the inner surface of the vitelline membrane. Ruffled membranes are described, comparable to those reported byABERCROMBIE andAMBROSE for other types of cells growing in tissue culture. 2. The ruffled membranes, which have been examined both by scanning and transmission electron microscopy, are visible as broad, flattened processes which adhere closely to the inner surface of the vitelline membrane. 3. The inner and outer surfaces of the vitelline membrane, and the endodermal surface of the area opaca, have also been examined by scanning electron microscopy.