The Mobile Agent (MA) model seems to provide one of the most suitable technology for distributed systems to integrate the Internet in a synergic way. One of the problems that should be faced when considering mobile agents for distributed applications is the lack of a thorough model capable of describing the Internet world composed of interconnected networks, each of them with their peculiar policies (for administrative, management and security purposes). We propose a Mobile Agent system based on a model designed to consider and favour aggregations of abstract and protected (network) domains: the use of this model makes easy the development of Internet applications. The paper describes the MAMA system (Melding Abstractions with Mobile Agents) and its implementation in the Java language. An application for distributed monitoring provides an example of the results achieved within the MAMA system.