The “species” are the appearances, especially those of bread and wine, after the Eucharistic Consecration. “The term ‘species’ is used by the Council of Trent to identify the accidents, i.e., the size, weight, color, resistance, taste, and odor of bread, which remain exactly the same after transubstantiation. They are not mere appearances as though these physical properties were unreal. But they are appearances because after the Consecration they lack any substance that underlies them or in which they inhere” (Modern Catholic Dictionary). (For Advanced Course lesson 20.)