De Bary spent much time studying the morphology of fungi and noticed that certain forms that had been classified as separate species were actually successive stages of development of the same organism. De Bary studied the developmental history of Myxomycetes (slime molds), and thought it was necessary to reclassify the lower animals. He first coined the term Mycetozoa to include lower animals and slime molds. In his work on Myxomycetes (1858), he pointed out that at one stage of their life cycle (the plasmodial stage), they were little more than formless, motile masses of the substance that Félix Dujardin (1801–1860) had called sarcode (protoplasm). This is the fundamental basis of the protoplasmic theory of life.