Ultrastructures that emanate from the neural folds at the site of closure have been regarded as a secondary process in the frog. This is because wound healing which acts via actin purse-string contraction is thought to be the primary cause of closure in the frog neural tube . Adhesion of the neural tube and epidermis have been suggested to be separate events based upon the observation that the epidermal ectoderm is still able to migrate and cover the open neural tube in both the chick and the frog [302, 305]. However, the issue of whether or not the neural folds could adhere even in the absence of epidermal fusion in both the chick and the frog has yet to be answered.