coelenteron
1. their tissues, composed of two cell layers, surround a cavity known as a coelenteron (gastrovascular cavity), which is the basic internal organ.
身体大致呈杯形,由内、外胚层组成的组织围绕著一个空腔(腔肠),这是它基本的内部器官,此外并无明确的呼吸、循环和排泄器官。