THE IXADEQUACY OF THE CELL-THEORY. lOJ 



All higher organization is supposed to begin with cell-forma- 

 tion, and to reach its fullest expression in the mutuality of the 

 constituent cells. Whether the cytoplasm be regarded as 

 isotropic or as definitel}' organized, whether the hereditary 

 substance be identified with the egg as a whole, or with the 

 nuclear chromosomes alone, the cell-dogma is still supreme. 



Our microscopes resolve the organism into cells, and onto- 

 geny shows that the many cells arise from one cell ; hence, 

 the organism seems to be the product of cell-formation, and 

 the cleavage of the germ seems to be a building process. 

 The cell-theory points us to very definite units, as the ele- 

 ments of organization, and thus offers what has for a long time 

 appeared to be a rational basis for the investigation of life- 

 phenomena. All the search-lights of the biological sciences 

 have been turned upon the cell ; it has been hunted up and 

 down through every grade of organization ; it has been 

 searched inside and out, experimented upon, and studied in its 

 manifold relations as a unit of form and function. It has been 

 taken as the key to ontogeny and phylogeny, and on it theories 

 of heredity and variation have been built. For a long time it 

 has been regarded as a decisive test of homology in germ- 

 layers, tissues, and organs. Fundamental distinctions have 

 been made between z^/rrt-cellular and ////^/--cellular organiza- 

 tion, between unicellular and multicellular organisms and 

 organs, between cellular and acellular growth and develop- 

 ment, between the processes of fission and regeneration in the 

 protozoan and the metazoan, between differentiation zuitJiin 

 the cell and ajuoiig cells, between the formative forces which 

 shape the infusorian and those which act in a many-celled 

 organism. 



An organism of many cells is supposed to differ from one of 

 one cell, somewhat as a complex molecule differs from a simple 

 one. The complex unit bears not only the structure of its in- 

 dividual parts, but also a totally new structure formed by the 

 union of these parts. In like manner the organism is fancied 

 to carry at least two distinct organizations, the organization of 

 the separate cells and that of the cells united. The higher 

 organization thus differs, qualitatively, from the lower, so that 



