Haeckel formulated his theory as "Ontogeny recapitulates phylogeny". The treatment is based on the largely discredited hypothesis that ontogeny recapitulates phylogeny. This theory can be encapsulated as "ontogeny recapitulates phylogeny". He produced an early phylogenetic tree revealing the ontogeny and phylogeny of vertebrate embryos. The idea that ontogeny recapitulates phylogeny has been applied to some other areas. Felid forelimb development during ontogeny (changes during growth) has remained tightly constrained. Zingiberales demonstrate an evolutionary trend in the ontogeny of the perianth (sepals and petals). The social pre-wiring hypothesis refers to the ontogeny of social interaction. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism. Flat headed individuals saw little cranial damage supporting their juvenile stage ontogeny. Scientific studies have focused on their ontogeny, biomechanics and ecology, among other subjects. Lizards often exhibit allometric changes during their ontogeny. Flower ontogeny uses a combination of genes normally responsible for forming new shoots. However, growth bands are weakly expressed later in ontogeny. This ratio changes during ontogeny and in diseased states (such as leukemia).