196 Proceedings of the Royal Physical Society. 



as shown in the female and male sexes respectively, and 

 have suggested the same antithesis as dominating plants and 

 animals. While admitting this antithesis as far as kata- 

 bolism is concerned, it seemed that a somewhat different 

 expression of the contrast of the metabolism in animals and 

 plants, which would depend on the kind of anabolism along 

 which each had separately specialised, might give a clearer 

 view of the matter. Katabolism cannot take place without 

 corresponding anabolism, and the greater the katabolism the 

 greater must be the anabolism. Although anabolism may 

 take place with accompanying greater or less loss of energy, 

 it seems that in all the higher forms of life in which we find 

 the greatest recurring katabolism, that here also we have 

 the greatest anabolism. The chief difference between the 

 metabolism in plants and animals appears to be, that the 

 plant is anabolic and wastes but little on katabolism, while 

 the animal wastes enormously in katabolism, but has great 

 powers of anabolism to keep pace with it. If we suggest 

 that in animals the specialisation is dominated by an 

 increasing tendency to instability in the products of 

 anabolism, or by mere simile, the production of living 

 material whose organic molecule is more and more complex 

 and unstable; and in plants, on the contrary, that the 

 specialisation is dominated by an increasing tendency to 

 stability in the products of anabolism, or the production of 

 living material whose organic molecule is increasingly more 

 simple and stable, the question of the loss of potential which 

 we were discussing above will be partly governed by a 

 different factor from the point at which animals and plants 

 divercjed in the course of evolution. It would follow that, 

 previous to this point in the evolution of organisms, the type 

 of specialisation would not have had the same direction as 

 that in which plants have since evolved. The primitive 

 protoplasm must have first acquired that instability of 

 anabolism, or elaboration of its substance, which allowed of 

 the essential factors of life. To those who believe in the 

 evolution of organisms from unorganised matter, this primi- 

 tive organised structure must have been capable of anabolising 

 from unorganised material before the first true plants were 



