re probably only fixed pseudopodia.

But scientists are far from agreed on the value of explanations and
schemas of this sort. Chemists have pointed out that even in the
organic--not to go so far as the organized--science has reconstructed
hitherto nothing but waste products of vital activity; the peculiarly
active plastic substances obstinately defy synthesis. One of the most
notable naturalists of our time has insisted on the opposition of two
orders of phenomena observed in living tissues, _anagenesis_ and
_katagenesis_. The role of the anagenetic energies is to raise the
inferior energies to their own level by assimilating inorganic
substances. They _construct_ the tissues. On the other hand, the actual
functioning of life (excepting, of course, assimilation, growth, and
reproduction) is of the katagenetic order, exhibiting the fall, not the
rise, of energy. It is only with these facts of katagenetic order that
physico-chemistry deals--that is, in short, with the dead and not with
the living.[15] The other kind of facts certainly seem to defy
physico-chemical analysis, even if they are not anagenetic in the proper
sense of the word. As for the artificial imitation of the outward
appearance of protoplasm, should a real theoretic importance be attached
to this when the question of the physical framework of protoplasm is not
yet settled? We are still further from compounding protoplasm
chemically. Finally, a physico-chemical explanation of the motions of
the amoeba, and _a fortiori_ of the behavior of the Infusoria, seems
impossible to many of those who have closely observed these rudimentary
organisms. Even in these humblest manifestations of life they discover
traces of an effective psychological activity.[16] But instructive above
all is the fact that the tendency to explain everything by physics and
chemistry is discouraged rather than strengthened by deep study of
histological phenomena. Such is the conclusion of the truly admirable
book which the histologist E.B. Wilson has devoted to the development
of the cell: "The study of the cell has, on the whole, seemed to widen
rather than to narrow the enormous gap that separates even the lowest
forms of life from the inorganic world.[17]"

To sum up, those who are concerned only with the functional activity of
the living being are inclined to believe that physics and chemistry will
give us the key to biological processes.[18] They have chiefly to do, as
a fact, with p