ergone, indicate, more
or less clearly, the first changes which took place in the series of
forms through which the existing form has been reached. Describing, in
successive groups of plants, the early transformations of these
primitive units, Sachs[44] says of the lowest _Algae_ that "the
conjugated protoplasmic body clothes itself with a cell-wall" (p. 10);
that in "the spores of Mosses and Vascular Cryptogams" and in "the
pollen of Phanerogams" ... "the protoplasmic body of the mother-cell
breaks up into four lumps, which quickly round themselves off and
contract, and become enveloped by a cell-membrane only after complete
separation" (p. 13); that in the _Equisetaceae_ "the young spores, when
first separated, are still naked, but they soon become surrounded by a
cell-membrane" (p. 14); and that in higher plants, as in the pollen of
many Dicotyledons, "the contracting daughter-cells secrete cellulose
even during their separation" (p. 14). Here, then, in whatever way we
interpret it, the fact is that there quickly arises an outer layer
different from the contained matter. But the most significant evidence
is furnished by "the masses of protoplasm that escape into water from
the injured sacs of _Vaucheria_, which often instantly become rounded
into globular bodies," and of which the "hyaline protoplasm envelopes
the whole as a skin" (p. 41) which "is denser than the inner and more
watery substance" (p. 42). As in this case the protoplasm is but a
fragment, and as it is removed from the influence of the parent-cell,
this differentiating process can scarcely be regarded as anything more
than the effect of physico-chemical actions: a conclusion which is
supported by the statement of Sachs that "not only every vacuole in a
solid protoplasmic body, but also every thread of protoplasm which
penetrates the sap-cavity, and finally the inner side of the
protoplasm-sac which encloses the sap-cavity, is also bounded by a skin"
(p. 42). If then "every portion of a protoplasmic body immediately
surrounds itself, when it becomes isolated, with such a skin," which is
shown in all cases to arise at the surface of contact with sap or water,
this primary differentiation of outer from inner must be ascribed to the
direct action of the medium. Whether the coating thus initiated is
secreted by the protoplasm, or whether, as seems more likely, it
results from transformation of it, matters not to the argument. Either
way the action of the med