The end-to-end attribute of the Internet enables easy modification and deployment of applications running at the host. Competition among these applications promotes the development of the Internet. However, new protocols related to the core layer, and network routers and switches are often hard to successfully implement. This paper proposes an Evolvable Internet Architecture (EIA). It suggests that new network architectures can be plugged into network equipment or into a host through interfaces provided by EIA for network experimentation or actual network deployment. Users can independently select network architectures, and use one or some of these architectures at the same time. The diversity provided by EIA will promote the evolution of the Internet.