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) The Silkie (novel) The Silkie is a fix-up science fiction novel by A. E. van Vogt, first published in complete form in 1969. The component stories had previously been published in "Galaxy Science Fiction" magazine. Taking its inspiration from the Celtic legend of the Selkie, the novel describes a race of apparent humans with the ability to change into other forms. One, like the Selkie of legend, can live underwater. Another can survive and travel unprotected in outer space. In all three forms the Silkies can wield mental powers over energy to some degree. After a prologue which purports to