2I 4 



THE EVOLUTION OF SEX. 



SUMMARY. 



I. Growth is characteristic of living organisms, though analogous processes 

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

 matter. As certain as the fact of growth is the deriniteness of its limit alike for 

 cell and for organism. 



II. Spencer has analyzed the limit of growth, in terms of the continual 

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



III. 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. 



IV. 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. 



V. Throughout organic life there is a contrast or rhythm between growth 

 and multiplication, between nutrition and reproduction, corresponding to the 

 fundamental organic seesaw between anabolism and katabolism. 



VI. 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 reproduc- 

 tion are fundamentally nearly akin. 



VII. The contrasts between continuous growth and discontinuous multiplica- 

 tion, between asexual and sexual reproduction, between parthenogenesis and 

 sexuality, between alternating generations, are all different expressions of the 

 fundamental antithesis. 



LITERATURE. 



Spencer, Principles of Biology ; and Haeckel, Generelle Morphologic 



