A Criticism of the Cell-Theory; being an Answer to Mr. Sedgwick's ...

A CRITICISM OF THE CELL-THEORY. 151
standing the structure of protoplasm, and it might be said
that, if we know nothing of the component, it is useless to
make assertions about the compost; but it will at least be
useful to criticise the attempts which have been made.
Hertwig gives this definition, which is the same as that
originally given by Max Schulze. A cell is a corpuscle of
protoplasm in which is contained a specially organised constituent,
the nucleus. (Die Zelle ist ein kliitnpchen von Protoplasma,
das in seinen Innern einen besonders geformten
Bestandtheil, den Kern (Nucleus) einschliesst.) This at first
sight seems satisfactory enough, but the more one examines
it, the less satisfactory does it appear, in view of the different
kinds of organisms which are usually described as single cells.
If a corpuscle containing a nucleus is a cell, is a corpuscle
Containing two or more nuclei also a cell ? And still more, is
a large mass of protoplasm containing many nuclei to be
regarded as a cell ? Such a mass, I mean, as Botrydium,
Caulerpa, or Codium, or even Pelomyxa. By many authors
these organisms are regarded as single multinucleate cells, but
I am far from being convinced that this is a right view of the
case. 1
If there is one thing more than another which has come
into prominence as the result of recent research, both botanical
and zoological, it is the fundamental importance of the
nucleus to cell life. So many minute organisms, which at one
1 With regard to the argument which follows, I would remind my readers
that Hackel, thirty years ago, clearly expressed the view which I am now
urging (see his " Allgemeine Anatomie den Organismen," forming the first
part of the ' Generelle Morphologie,' p. 296). " Es muss hierbei ausdriicklich
errinert werden, dass wir unter eine Zelle nur einen Plasma-Klumpen mit
einem Kerne verstehen konnen. Der haufig gebrauchte Ausdruck einer
' mehrkernigen Zelle' ist eine Contradictio in adjecto, da ja eben nur die
Einheit des Kerns die individuelle Einheit der Zelle als eines Elementar-
Organismus bedingt. Jeder Plasmaklumpen, der mehr als einen Kern
umschliessfc, moge er nun von einer Membran umhiillt sein oder nicht, ist eine
Vielheit von Zellen, und wenn diese Yielheit eine bestimmte einheitliche
Form besitzt, so haben wir sie als Zellenstock zu dem Range eines Organes
erster Ordnung zu erheben." This view, however, has been controverted by
many authorities, as will appear further on.