Schwann stated the following 

Schwann reported that animal cells had a thin outer layer which is today known as plasma membrane. He also concluded that plant cells have cell wall but not animal cells. He also proposed a hypothesis that the bodies of animals and plants are composed of cells and products of cells. Schleiden stated that plant tissues are composed of cells. Rudolph Virchow stated that cells arise from preexisting cells and modified cell theory to give the present shape.