THE ENERGY OF EVOLUTION. 485 



to the modified or "grade" growth force, and to term 

 the inherited or "simple' type of growth force, em- 

 phytism. 1 As a matter of fact, pure emphytism can 

 only be observed in the embryos of sexless or parthe- 

 nogenetic origin, and in the repair of tissues. 



Ryder has called the exhibition of growth-energy 

 ergogenesis, and he calls attention to the fact that it 

 appears under two aspects. In the first, ergogenesis 

 is due to mechanical causes resident in the organism 

 exclusively, and consists of the physical tensions in- 

 herent in protoplasm under all the conditions of 

 growth. With these the growth-energies have to 

 reckon, as they are the conditions which underlie them. 

 They are not, however, strictly speaking, growth- 

 energies, but would be exhibited by any similar col- 

 loid under similar conditions. To the movements due 

 to physical causes under these circumstances, Ryder 

 gives the name of Statogenesis. 2 The second aspect 

 of the energies necessary to growth is present under 

 the two forms already referred to, as emphytism and 

 bathmism. The latter class, or interference energies, 

 are naturally differentiated into those which are due 

 to physical (or chemical) external agencies (molecular 

 movements), and those that are due to molar move- 

 ments as expressed in tissues, as impact, strain, etc. 

 To the former I have given the name of physiobath- 

 mism, to the latter, kinetobathmism. 3 



The relations of these forms of energy may be rep- 

 resented in tabular form as follows : 



II have supposed in a late paper (American Naturalist, 1894, p. 212) that 

 this is the statogenic energy of Ryder. This mistake has been corrected. 



2 Proceedings American Philosophical Society, 1893, p. 194. 



^American Naturalist, 1894, p. 214. The two types of growth are then 

 physiogenesis and kinetogenesis. (Origin of the Fittest, 1887, p. 423.) 



