No. :>!):?] 



THE EVOLUTION OF THE CELL 



281 



Appendix A.— The Cell-Theory 

 The most recent attack on the Cell-theory, as it is under- 

 stood by the majority of modern biologists, lias been made 

 by M r. I )obell, who, if I understand him rightly, refuses to 

 admit any homology between the individual Protistan or- 

 ganism and a single cell of the many that build up the 

 body of a Metazoon. On the contrary, he insists that the 

 Protist is to be regarded as homologous with the Metazoan 

 individual as a whole. On these grounds he objects to 

 Protista being termed "unicellular" and insists that the 

 term "non-cellular" should be applied to them. 



As regards the cellular nature of the Protista, it is one 

 of niv aims in this address to show that amongst the 

 Protista all stages of the evolution of the cell are to be 

 found, from primitive forms in which the body can not be 

 termed a cell without depriving the term "cell" of all de- 

 finable meaning, up to forms of complex structure m 

 which all the characteristic features of a true cell are fully 

 developed. Thus in the Protozoa we find the protoplas- 

 mic body differentiated into nucleus and cytoplasm ; the 

 nucleus in many cases with a structure comparable m 

 every detail to that of the nucleus of an ordinary body- 

 cell in the Metazoa; reproduction taking place by division 

 of the bodv after a karyokinetic nuclear division often 

 quite as complicated as that seen in the cells of the Metazoa 

 and entirely similar both in method and ^in detail^; and 



