as demonstrated by Heinrich de
Bary and by Max Schultze that the two are to all intents and purposes
identical. Even earlier Remak had reached a similar conclusion, and
applied Von Mohl's word protoplasm to animal cell contents, and now this
application soon became universal. Thenceforth this protoplasm was
to assume the utmost importance in the physiological world, being
recognized as the universal "physical basis of life," vegetable and
animal alike. This amounted to the logical extension and culmination
of Schwann's doctrine as to the similarity of development of the two
animate kingdoms. Yet at the same time it was in effect the banishment
of the cell that Schwann had defined. The word cell was retained, it
is true, but it no longer signified a minute cavity. It now implied,
as Schultze defined it, "a small mass of protoplasm endowed with the
attributes of life." This definition was destined presently to meet with
yet another modification, as we shall see; but the conception of the
protoplasmic mass as the essential ultimate structure, which might or
might not surround itself with a protective covering, was a permanent
addition to physiological knowledge. The earlier idea had, in effect,
declared the shell the most important part of the egg; this developed
view assigned to the yolk its true position.

In one other important regard the theory of Schleiden and Schwann now
became modified. This referred to the origin of the cell. Schwann had
regarded cell growth as a kind of crystallization, beginning with the
deposit of a nucleus about a granule in the intercellular substance--the
cytoblastema, as Schleiden called it. But Von Mohl, as early as 1835,
had called attention to the formation of new vegetable cells through the
division of a pre-existing cell. Ehrenberg, another high authority of
the time, contended that no such division occurs, and the matter was
still in dispute when Schleiden came forward with his discovery of
so-called free cell-formation within the parent cell, and this for a
long time diverted attention from the process of division which Von Mohl
had described. All manner of schemes of cell-formation were put forward
during the ensuing years by a multitude of observers, and gained
currency notwithstanding Von Mohl's reiterated contention that there
are really but two ways in which the formation of new cells takes
place--namely, "first, through division of older cells; secondly,
through the formation of