it is proposed that the completion of both growth and differentiation , in highly specialized progressively evolving multicellular organisms , is achieved throughout two separated but sexually interacting populations of cells ( bi-clonal model ) : 1 ) the germ line , seated in an obligatory axial position , required for the generation of cytoplasmic replicons , is the source of travelling vectors ( spermatozoa , lymphocytes ... )
C0007634
cells
C0010834
cytoplasmic