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 Bird Lover the lai develops somewhat differently: instead of a happy ending, the lai ends in tragedy. A "sophisticated rationalization" of the type is found in Chrétien de Troyes's "Lancelot, the Knight of the Cart", where Lancelot appears at Guinevere's heavily barred window and cuts his fingers bending the bars back. In French scholarship, this type is often referred to as ""loiseau bleu"" or "the blue bird", so named for a story by Madame d'Aulnoy. The Bird Lover The Bird Lover, also known as The Prince as Bird, is a type of narrative structure in folklore, no. 432 in the Aarne–Thompson classification