GROWTH AND REPRODUCTION. 23 1 



SUMMARY. 



1. Growth is characteristic of living organisms, though analogous pro- 

 cesses occur at the inorganic level. Hunger is an essential characteristic of 

 living matter. As certain as the fact of growth, is the definiteness of its 

 limit alike for cell and for organism. 



2. Spencer has analysed the limit of growth, in terms of the continual 

 tendency that increase of mass must have to outrun increase of surface. 



3. Cell-division at the limit of growth, at the maximum or optimum of 

 size, restores the balance between mass and surface. The actual mechanics 

 of the process are at present beyond analysis. 



4. Spencer's analysis may be restated in protoplasmic terms. Growth 

 expresses the preponderance of anabolism ; increase of mass, with less 

 rapid increase of nutritive, respiratory, and excretory surface, involves a 

 relative predominance of katabolism. The limit of growth occurs when 

 katabolism has made up upon anabolism, and tends to outstrip it. What 

 is true of the unit, applies also to the entire multicellular organism. 



5. Throughout organic life there is a contrast or rhythm between 

 growth and multiplication, between nutrition and reproduction, corre- 

 sponding to the fundamental organic see-saw between anabolism and 

 katabolism. 



6. This contrast may be read in the distribution of organs, in the periods 

 of life, and in the different grades of reproduction. Yet nutrition and 

 reproduction are fundamentally nearly akin. 



7. The contrasts between continuous growth and discontinuous multi- 

 plication, between asexual and sexual reproduction, between partheno- 

 genesis and sexuality, between alternating generations, are all different 

 expressions of the fundamental antithesis. 



LITERATURE. 

 Spencer, Principles of Biology ; and ILeckei., Generelle Morphologic. 



