摘要: This chapter describes embryos and their evolution. Animal evolution has produced is producing a great variety of animal forms. The ways in which this variation appears the life history animals concerned part province embryology. Caenogenetic modifications are those variations that benefit young form, embryo or larva, have no particular significance for adult. Very often they lost at hatching, birth, metamorphosis. converse situation, paedomorphosis, early acquisition adult state while organism still larval general body form. insects probably derived by paedomorphosis from form resembling modern millipedes, six-legged stage vertebrates may been echinoderm-like ancestors retention characters. In many primates, especially anthropoid apes man, be said to neotenous mammals. Deviation, on other hand, changes adaptations, primarily adults, meet requirements. Because conservative nature developmental changes, stages two related usually resemble one another more than later stages.