TISSUE INTERACTION AND FORMATION OF FIRST ERYTHROBLASTS OF CHICK EMBRYO

1. 1. The ectomesoderm of the area vasculosa of the chick embryo of the definitive primitive streak stage was cultured with or without endoderm present on the opposite side of a Millipore filter. 2. 2. The development of blood islands was much more prominent in the ectomesoderm combined with endoderm across the filter than in control experiments without endoderm. 3. 3. No exchange of cells, however, between the interacting tissues was observed. A stainable material penetrating about one-fourth of the thickness of the filter was observed. 4. 4. The ectomesoderm taken from the posterior half of the area opaca cultured in direct contact with the endoderm from a blood island free area anterior to the head fold showed a prominent development of blood islands. 5. 5. The ectomesoderm cultivated in contact with the endoderm lethally treated with heat did not show distinct blood islands. The data are discussed in relation to the nature of tissue interactions. © 1969.