It will be observed that all this elaboration of the original theory of germ-plasm—an elaboration which is largely derived from the speculative writings of Nägeli—serves no other purpose than that of indicating what Professor Weismann now regards as the most probable _mode_ in which germ-plasm undergoes its modification into the various kinds of somatic-cells. For, inasmuch as the idio-plasms-B of all somatic-cells are originally derived from that of the germ-cell, and inasmuch as each expends its formative energies exclusively in constructing and controlling the cells which, as idio-plasms-A, they respectively inhabit, it is still the germ-plasm of the original germ-cell that is finally converted into the various tissues which together constitute the soma—notwithstanding that, in order thus to become transmuted into body-substance, or somato-plasm,it must pass through the sundry intermediate stages of idio-plasm-B, idio-plasm-A, and cytoplasm, of any given ontogenetic stage. Hence I do not see that it makes any substantial difference to Weismann’s theory of heredity, whether we speak of germ-plasm being converted into “somato-plasm,” or into “idio-plasm” _plus_ “somatic-idio-plasm,” _plus_ “cytoplasm.” But as Weismann himself thinks that it does make some great difference whether we adhere to his original generic term “somato-plasm,” or adopt his newer and more specific terms as just enumerated, I append _in extenso_ the most recent exposition of his views upon this subject[8].