Cytology, Homology and Phylogeny-A Note on "Organic Design"

The origins of the resemblances between living organisms are discussed. It is suggested that at the lower levels of organization, exemplified by biochemical characters, cell organelles, and early embryonic forms, similarities do not necessarily imply common ancestry; independent origin is equally probable. The reasons for advocating this view are given and the problems which it raises in attempting to define the term `homology' are examined. The relevance of the idea to discussions of the phylogeny of the lower organisms is briefly considered.