306 SCIENCE PROGRESS 



led to the conviction that the earliest forms of life were 

 extremely minute ultramicroscopic particles consisting of chro- 

 matin alone. I do not lay claim to any novelty in this view; 

 I put it forward simply because I believe it to be true. In 

 the process of gradual evolution and adaptation to divers 

 conditions of existence these minute chromatin-particles formed 

 round themselves envelopes and coats of substance other than 

 chromatin and so gave rise to cytoplasmic elements. As the 

 body was thus increased in size, the next step would be an 

 increase in the number of granules of chromatin contained in 

 it. At this stage the bacterial type of organisation could have 

 arisen by the secretion of a firm membrane at the surface of 

 the body enclosing one or more grains of chromatin (chromidia) 

 in a small amount of cytoplasm. I am far from regarding the 

 bacteria as the earliest or simplest possible forms of life, as 

 some authorities seem to hold ; they appear to me rather to 

 represent a type of organisation which arose very early in the 

 evolution of living beings, long before the divergence into 

 animals and plants which dominates modern terrestrial life ; a 

 type in which the characteristic limiting membrane has in- 

 hibited further advance in evolution and has restricted their 

 structural differentiation within a narrow range. I consider 

 this at least a more feasible interpretation of the nature of 

 the bacteria than the view held by many that they are to be 

 derived from organisms primitively of cellular structure which 

 have become highly specialised for a parasitic or saprophytic 

 mode of life. 



The absence, on the other hand, of a rigid membrane or 

 cuticle round the bodies of some of our imagined primitive 

 organisms would permit the formation of a greater amount of 

 cytoplasmic substance and an increase in the number of chroma- 

 tin-erains in a larger body. Thus would be possible an organism 

 of dimensions relatively large, indeed gigantic as compared with 



of the nucleus, that are characteristic of the same, are simpler in construction than 

 the protein-molecules of the cytoplasm and, therefore, most likely more primitive ; 

 (2) that the protein-molecules of the cytoplasm, that are characteristic of it, are 

 more complex than those characteristic of the nucleus and less likely to be 

 primitive ; (3) that the amino-acid characteristic of the chief nuclear protein is an 

 open chain free from complexity, whist the amino-acids characteristic of the 

 cytoplasm are closed ring compounds that could only arise from chemical com- 

 pounds of the same type as that characteristic of the nucleus. These facts, I 

 believe, have an important bearing on your subject." 



