A ORITICISM 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 con- 
stituent, the nucleus. (Die Zelle ist ein kliimpchen von Proto- 
plasma, 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.! 
If there is one thing more than another which has come 
into prominence as the result of recent research, both botani- 
cal 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 kénnen. Der hiaufig gebrauchte Ausdruck einer 
‘mebrkernigen 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 
umschliesst, mége er nun von einer Membran umhiillt sein oder nicht, ist eine 
Vielheit von Zellen, und wenn diese Vielheit 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, 
