Primary invagination can be disrupted by treating embryos with monoclonal antibodies that recognize a family of proteins called fibropellins that reside in the apical lamina. Panels B and C in the top row are embryos treated with two different monoclonals; the control invaginates normally (A). As control embryos invaginate (A, bottom row), the antibody-treated embryos can only muster a small indentation (B,C, bottom row). Photos are courtesy of Dr. Robert Burke, Univ. of Victoria.