Many biological facts are irreconcilable with the assumption that larvae and adults evolved from the same genetic stock. The author of this book draws attention to these, and presents his alternative hypothesis that larvae have been transferred from one taxon to another.

In his previous book (Larvae and Evolution, 1992), the author used larval transfer to explain developmental anomalies in eight animal phyla. In the present book, he claims that the basic forms of all larvae and all embryos have been transferred from foreign taxa. This leads to a new, comprehensive theory on the origin of embryos and larvae, replacing the discredited 'recapitulation' theory of Haeckel (1866). Metamorphosis, previously unexplained, represents a change in taxon during development.