DELETION-TRANSPLANTATION EXPERIMENTS ON EMBRYOS OF FUNDULUS-HETEROCLITUS .2. ANTERIOR EMBRYONIC SHIELD

Experiments are described in which the differentiative capacity of the anterior embryonic shield of the teleost. Fundulus heteroclitus, was investigated by means of deletion‐transplantation techniques. The anterior embryonic shield, deleted from gastrula stages and transplanted into the pericardial chamber of an older embryo, exhibits growth and differentiates structures appropriate only to anterior head. All germ layers are involved in both the operation and subsequent differentiation. The donor embryos, in general, develop normally except for striking deficiencies in forebrain and eyes. Both donors and grafts indicate increasing specificity of determination in the cells of the anterior shield as development proceeds from early to late gastrula. The experiments are discussed from the standpoint of their elucidation of localization of developmental potencies in the anterior embryonic shield. Two unexpected effects of graft on host are described and briefly discussed: (1) the differentiation of glandular cells in the host pericardial epithelium in the immediate vicinity of the graft, tentatively labeled an “induction,” and (2) a deleterious systemic effect of the graft on the host embryo. Both of these effects occurred in a significant number of cases but appear to be unrelated to each other and are, as yet, unexplained. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company