As Rashaverak explains, the time of humanity as a race composed of single individuals with a concrete identity is coming to an end. The children's minds reach into each other and merge into a single vast group consciousness. If the Pacific were to be dried up, the islands dotting it would lose their identity as islands and become part of a new continent; in the same way, the children cease to be the individuals which their parents knew and become something else, completely alien to the "old type of human".