24 SCIENCE PROGRESS. 



and so close that we are almost warranted in drawing the 

 conclusion that the measure of the resemblance will afford a 

 criterion as to the relative degree of importance to be 

 attached to this or that phenomenon of cell life. 



It seems almost certain that this similarity is to be 

 interpreted as the result of the evolution along parallel 

 lines of a particular structural arrangement, or, to put it in 

 another way, as being the outcome of the continuous opera- 

 tion of similar forces upon an essentially similar proto- 

 plasmic structure. No doubt all the change manifested in 

 protoplasm is ultimately to be ascribed to the effects of 

 forces upon its own material substance ; the special point 

 of interest here lies in the similarity of the results. It 

 cannot be due to mere accident that the stages in the develop- 

 ment of the spermatozoa of a newt should bear a closer 

 resemblance to the corresponding divisions in the pollen- 

 mother-cell of a lily than they do to the rest of the tissue 

 cells in the body of the same newt. 



In the present article it is not my purpose to attempt to 

 summarise the vast amount of detail which has accumulated 

 within recent years ; my aim is rather to try to indicate the 

 general directions in which the results seem to be tending, 

 and to point out the kind of evidence on which the current 

 views are based. And although I am here especially dealing 

 with the botanical aspect of the questions involved, it will 

 be clear from what has been already said that it will be 

 impossible, and certainly not desirable, to ignore the in- 

 vestigations which have been prosecuted by the zoologists. 



And in order to make clear that which is to follow, it 

 may not be superfluous to recapitulate the general relations 

 of nucleus and cell protoplasm as commonly received at the 

 present time. The essential character of all cells, whether 

 animal or vegetable, and whether they exist as free inde- 

 pendent organisms, or whether they form more or less 

 highly differentiated colonies, consists in this, the association 

 of a nucleus with a certain amount of cell protoplasm (com- 

 monly called Cytoplasm, to distinguish it from the nuclear 

 protoplasm). And this is equally true, so far as we have 

 means of determining the question, in the case of those 



