Mar. 1901.] BOTANICAL SOCIETY OF EDINBURGH 51 



accomplishment of the fundamental functions of assimilation 

 and reproduction. These conditions are the following : — 



(1) The molecule must be suited by its constitution to 

 be transformed, by aid of assimilation, in such a manner as 

 to split into molecules of a structure like its own. 



(2) Food substances must always be present. 



(3) The nutritive substances and the secondary products 

 (secreta) must not react to their mutual destruction. 



(4) The reactions of assimilation must follow in a regular 

 order. 



(5) Physical conditions (light, heat, etc.) must be favour- 

 able for each reaction. 



The first is the intrinsic condition, the others are the 

 extrinsic conditions. The last four are the conditions of 

 assimilation ; while all, but more particularly the first, are 

 conditions of reproduction. 



All these conditions are shown to be realised in nature 

 for the living molecule ; and the discussion of the fifth 

 condition brings out the great complexity of the living 

 molecule, and also its very unstable character. 



It will conduce to clear understanding to give the 

 author's summary of the results arrived at up to this 

 point. Assimilation and reproduction are both equally 

 chemical phenomena, explainable by the known laws of 

 chemistry, " Eeproduction is the fission of a biomolecule, 

 which, after a series of assimilatory changes, undergoes 

 dMoublenient into other molecules having the same struc- 

 ture as the original molecule." " Life is not absolute, it 

 is only relative ; it is the resultant of certain intimate 

 relations which must exist between the constitution of the 

 living molecule (intrinsic condition of life) and the physico- 

 chemical conditions of environment (extrinsic conditions of 

 life.) " 



Apart from its novelty and ingenuity, one is struck by 

 the completeness, definiteness, and simplicity of our author's 

 explanation of the phenomena of assimilation, or formation 

 of living matter, as contrasted with the obscurity that 

 prevails in most other theories. Compare it with that in 

 plant physiology, where the proteids formed during con- 

 structive metabolism are, in some unexplained way, 

 transformed into living substance by the already existing 



