THE president's ADDRESS. 351 



Chlamydozoa are difficult, if not impossible, to cultivate on the 

 ordinary bacterial culture-media. 



Returning now after this digression to the general problem, it 

 may be said that the more minute a living body, the more it 

 appears to be stripped, as it were, of all cytoplasmic elements 

 and to be reduced finally to chromatin alone. It is, of course, 

 impossible to analyse accurately the structure of the minutest 

 organisms, and statements with regard to them must be made 

 with the utmost caution in the present state of knowledge ; but 

 it can at least be asserted that while many organisms are known 

 which consist mainly, if not entirely, of chromatin, there are 

 none known which consist solely of cytoplasm, and in which the 

 chromatin is entirely absent. 



The conclusion which I, personally, draw from the facts which 

 have been summarised briefly with regard to the living substance 

 is that the primary living substance, the primumi vivens, is 

 chromatin ; and from that I draw the further conclusion that 

 the simplest and earliest forms of life were minute particles of 

 chromatin, without other structural accessories, but nevertheless 

 capable of the essential and characteristic activities' of living 

 things that is to say, of assimilation, growth and reproduction 

 by fission. The first steps in the evolution of more complicated 

 forms of life were that these simple chromatin-particles formed 

 other structures around themselves, at first probably in the form 

 of simple protective envelopes, within which the cytoplasmic 

 matrix was gradually developed, until the body was large enough 

 to contain more than one chromatin-grain. This stage of struc- 

 tural complication is practically that seen in bacteria, speaking 

 generally. With further increase of the cytoplasm, proceeding 

 parallel with the concentration of the chromatin into a definite 

 nucleus, the cellular type of organisation is produced, the start- 

 ing-point for the evolution not only of the vast array of unicellular 

 organisms, but also of all the ordinary animals and plants. 



Now I would not have any of you go away with the impression 

 that my views with regard to the chromatin-particles represent 

 orthodox scientific doctrine. On the contrary, I believe that 

 most biologists at the present day would reject my theory most 

 emphatically and would consider me a heretic of the deepest dye 

 for putting forward such suggestions. In conversation, at least, 

 I have never found any one in the slightest degree inclined to fall 



