Doesn't seem that complicated if you think of the final stage as the first to evolve. After all, all multicellular beings build their bodies from scratch passin

Doesn't seem that complicated if you think of the final stage as the first to evolve. After all, all multicellular beings build their bodies from scratch passing through a number of intermediate stages. The surprising thing (for us) is that the intermediate stages can present themselves as viable organisms capable of living and feeding autonomously. In other words, there is nothing preventing an embryo from optimising one of its growth stages into a individual capable of feeding by itself before completing its transformation into its final shape.