INTRODUCTION 



who would deny this) that it is protoplasm which has, so to speak, 

 invented or produced chlorophyll. Accordingly, I incline to the 

 view that chlorophyll as we now know it is a definitely later evolu- 

 tion an apparatus to which protoplasm attained, and as a conse- 

 quence of that attainment we have the arborescent, filamentous, 

 foliaceous, fixed series of living things called plants. But before 

 protoplasm possessed chlorophyll it had a history. It had in the 

 course of that history to develop the nucleus with its complex 

 mechanism of chromosomes, and it had during that period to 

 feed. 



The suggestion has been made long ago (see article " Protozoa," 

 Ency. Brit, 6th edition), and appears to me not improbable, 

 that by whatever steps of change that high complex of organic 

 molecules which we call protoplasm the physical basis of life came 

 into existence, it very probably fed in the first few aeons of its 

 existence on the masses of proteid-like material which, it may be 

 supposed, were formed in no small quantity as antecedents to the 

 final evolution of living matter. If this were the case, the mode of 

 nutrition of the first living things must have been similar to that 

 of animals and unlike that of plants. At a later stage chlorophyll 

 was evolved, the decomposition of carbonic acid became possible, 

 and the Plant series was started. 



In accordance with this conception, we must look for the 

 representatives of the most primitive forms of life amongst the 

 minute Protozoa, possessing the simplest methods of nourishing 

 themselves by the digestion of already elaborated proteid. Such 

 are the Mycetozoa, which digest dead organic material by contact, 

 creeping in the form of naked plasmodia of many inches in area 

 over organic debris ; such, too, are the minute single cells of naked 

 protoplasm taking in particles of proteid food by extemporised 

 mouths and digesting them in the cell-body, whilst prehensile and 

 motor organs are furnished by the extension of the cell-protoplasm 

 in the form of lobose processes, radiating filaments, or single or 

 double vibratile flagella. The earliest plants, the Protophyta, 

 were, it seems most probable, derived from flagellate colony- 

 building Protozoa (similar to the Volvocinese), which had, at first 

 without discarding their animal-mode of nutrition (Zootrophic), 

 acquired the faculty of manufacturing chlorophyll and supplementing 

 their ingested nutriment by the decomposition of carbonic acid and 

 the fixation of nitrogen (Mixotrophic). The step from this to a 

 purely chlorophyll-given nutrition (Phytotrophic) was not a long 

 one, and indeed occurs in the life-history of some of the Flagellata 

 at the present day. With the establishment of pure Phytotrophic 

 nutrition ensued the formation by simple cell-division and element- 

 ary variation of cell-aggregation of filamentous green plants consist- 

 ing of chains of cells in single series ; to these followed networks of 



