Silkie the "SHH" gene, called the ZPA Regulatory Sequence (ZRS). This causes ectopic "SHH" expression in the anterior of the developing limb bud, leading to increased tissue growth and digits. While the feet of the Silkie display polydactyly, the wings have the standard tridactyly (three digit) arrangement. The Japanese Silkie initially develops additional digits in the wing as an embryo, but these are lost prior to hatching. The genetic cause behind Silkie polydactyly differs from those that cause polydactyly in the Dorking chicken breed, which is due to ectopic "FGF4" expression in the AER, with ectopic "SHH" a secondary effect. The
The Silkie (novel) contacts Earth and then leaves the ship, the boy reveals himself to be a malevolent shape-shifting alien. Cemp returns to Earth clandestinely in order to see his wife Joanne, but finds that the alien has taken on her form and is waiting in his house. The alien, known as the Kibmadine, displays Silkie-like control over energy during the fight which occurs after Cemp discovers the deception. The alien flees. With the aid of the main computer at Silkie Authority, Cemp analyzes his own sense-impressions of the Kibmadine. The result is a picture of a race which enters into an erotic-cannibalistic