Germ layers

1817

Germ layers

The book of science

Tom Sharp

Heinz Christian Pander embryology

Germ layers

Gastrulation of the blastulation

Embryogenesis

The phrase “ontogeny recaptitulates phylogeny” expresses the idea that the development of embryos repeats the evolutionary stages of the species; however, evolution of a new creature is more interesting than the accumulation of changes to the end of its ancestor’s development. Eggs are single-cells but animal eggs are not the same as single-celled organisms; they contain only half the chromosomes of the mother.

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