46 THEORY OF ORGANIC EVOLUTION. 



Idioplasm as bearer of the inheritable determinants; 

 (2) Spontaneous generation; (3) Causes of varia- 

 tion; (4) Determinants and visible characters, in 

 which the origin and function of the determinants 

 is presented; (5) Variety, race, "nutrition variety," 

 heredity and variation ; (6) Criticism of the Dar- 

 winian theory of natural selection, in which the 

 author urges seven objections to that theory; (7) 

 Laws of evolution of the plant kingdom ; (8) Alterna- 

 tion of generations from the standpoint of phylog- 

 eny ; (9) Morphology and classification as phyloge- 

 netic sciences; (10) A comprehensive summary of 

 the whole work, a translation of which is given in 

 the foregoing pages. 



In the first part of the work Nageli sets forth his 

 micellar theory of the structure of organized bodies. 

 This is one of his most important contributions to 

 science. Until recent years it has been the only 

 theory given in botanical text-books. At the pres- 

 ent time its only competitor is Strasburger's lamellar 

 theory, and even this has not superseded Nageli's 

 work to any great degree. 



The reader who may not be familiar with the 

 micellar theory will find the general idea from the 

 following brief sketch adapted from Vines's Plant 

 Physiology: 



"Nageli's micellar theory was developed from his study of 

 organized bodies, especially of cell walls and starch grains. 

 From the behavior of organized substance toward water 

 absorbed by it, he concluded that water does not penetrate 

 into the micellae, but only among them, thus merely separat- 

 ing them more from each other. He reasoned that if water 

 should penetrate into the micella, its structure would be 

 disintegrated. Hence he argued that organized bodies con- 

 sist of solid micellae, which, with their respective films of 



