Answer: Protostome development
Explanation: The ectoderm defines the formation of outer layer of the body such as skin, hair, mammary gland et cetera. The inner tissues of the body takes place and called as the endoderm
after the formation of ectoderm and endoderm, the interaction of these two layers helps in the formation of mesoderm.
The mesoderm forms the skeleton muscle, bone and connective tissue. This differentiation of the three germ layers takes place after protostome development.
