I endeavored in my _Generelle Morphologie_(1866) to draw the attention of biologists to these simplest and lowest organisms which have no visible organization or composition from different organs. I therefore proposed to give them the general title of monera. The more I have studied these structureless beings--cells without nuclei!--since that time, the more I have felt their importance in solving the greatest questions of biology--the problem of the origin of life, the nature of life, and so on. Unfortunately, these primitive little beings are ignored or neglected by most biologists to-day. O. Hertwig devotes one page of his three-hundred-page book on cells and tissues to them; he doubts the existence of cells without nuclei. Reinke, who has himself shown the existence of unnucleated cells among the bacteria (_beggiatoa_), does not say a word about their general significance. Bütschli, who shares my monistic conception of life, and has given it considerable support by his own thorough study of plasma-structures and the artificial production of them in oil and soap-suds, believes, like many other writers, that the "composition of even the simplest elementary organism from cell-nucleus and protoplasm" (the primitive organs of the cell) is indispensable. These and other writers suppose that the nucleus has been overlooked in the protoplasm of the monera I have described. This may be true for one section of them; but they say nothing about the other section, in which the nucleus is certainly lacking. To this class belong the remarkable _chromacea_ (_phycochromacea_ or _cyanophycea_), and especially the simplest forms of these, the _chroococcacea_ (_chroococcus_, _aphanocapsa_, _glœocapsa_, etc.). These plasmodomous (plasma-forming) monera, which live at the very frontier of the organic and inorganic worlds, are by no means uncommon or particularly difficult to find; on the contrary, they are found everywhere, and are easy to observe. Yet they are generally ignored because they do not square with the prevailing dogma of the cell.