556 THE HISTORY OF BIOLOGY 



allocated to the whole protoplasm of the egg; there must be a certain part 

 of them that is particularly responsible for the specific qualities. This con- 

 stituent of the cell Nageli calls idioplasma; he believes that through segmen- 

 tation it is imparted to every fresh cell and gives the latter its character; 

 it is through it that every organism is such as it is and not otherwise. The 

 idioplasma is, according to Nageli, a solid body, not semi-fluid like the rest 

 of the cellular mass, and it has, of course, its peculiar composition of micella, 

 the shape and size of which give rise to the most subtle calculations. All 

 evolution consists in changes in the micellas of the idioplasma, and these 

 changes go on incessantly, although they are not at once perceptible, for 

 the energy amassed through these changes is released intermittently, and 

 therefore the alterations in species likewise take place, not gradually, but 

 suddenly. 



From the structure of the idioplasma Nageli gradually passes to atomic 

 structure in general, and he here becomes involved in speculations as to the 

 atoms' being composed of still smaller particles, which are called " amera"; 

 of these latter the simple chemical basic elements are composed, and Nageli 

 builds up a kind of phylogeny for these elements, according to which the 

 heavy metals must have originated first, and afterwards the other elements 

 in succession. Further, he speculates upon the form of the atoms, upon ethe- 

 real atoms, ethereal heat, upon the impossibility of entropy, and various 

 similar subjects, which contemporary physics and chemistry had naturally 

 passed over in silence. 



His influence 

 Nageli's mechanical-physiological theory was his last work, so that he 

 concluded his life's activities, in spite of his expressed intention to deal with 

 natural phenomena on a mathematically exact basis, in a mass of thought- 

 constructions of just as impractical a nature as those of the master of his 

 youth, Hegel. His influence, however, has been of deep significance, not only 

 on account of the immense number of important facts that he established, 

 but also in the purely theoretical sphere. He was the first unreservedly to 

 venture to reject the doctrine of natural selection as the sole cause of the 

 evolution of life and to demand that it be replaced by another theory capable 

 of producing a more convincing confirmation by way of observation and 

 experiment. The " Vervollkommungskraff" on which he would base his ex- 

 planation of the origin of species was really nothing but a word, but behind 

 it there lay at any rate an insight into the fact that evolution is a quality 

 in life itself, not a movement that is thrust upon living creatures from out- 

 side. And in connexion therewith Nageli points out that life need not 

 necessarily evolve as a result of minute imperceptible variations, but the 

 changes might just as well take place suddenly and on a larger scale — an 

 idea which is certainly not very strongly brought out in him, but which 



