Chick embryo cells and halved embryos were successfully implanted into unfertilised eggs. Yolks containing implants were placed in recipient eggshells, covered by transparent vacuum-formed plastic cones and incubated for 72 h. 2. Dispersed cells were obtained from eggs expelled from the uterus or from eggs that had been laid. Implantation of these cells often resulted in aggregation and epithelial growth, in several cases with axial development. 3. Growth of implanted halved embryos of different ages was often observed, including one 10-somite embryo. Non-axial epithelia, sometimes with a central hole, a central fluid-filled cellular vesicle or a vesicle only, were also observed. 4. In another culture system, whole and halved embryos obtained from laid eggs were cultured on a vitelline membrane stretched across semi-solid egg albumen. During the 72 h incubation, axial development was observed only in whole embryos, while halved embryos grew either into epithelia containing fluid-filled cellular vesicles or into vesicles only. 5. It was found that daily drainage of the accumulating fluid from the embryo compartment encouraged axial development in halved embryos, and almost abolished vesicle formation. Holes were formed in half the embryos cultured on a vitelline membrane. 6. It appeared that physical and biological conditions could inflict serious malformations on the implants.
