No. 643] 



ORTHOGENESIS 



141 



Summary of Observations. —In the hard parts of ani- 

 mals orthogenesis is observed both in the origin of new 

 adaptive characters and in the evolution of proportions. 

 (1) The induction as to cause may be different in the 

 two cases. (2) In the origin of new adaptive characters 

 orthogenesis is attributable to definite germinal tend- 

 encies. (3) The origin of changes of proportion which 

 are subject to modification may be partly attributable 

 to Organic Selection. (4) There is positive disproof of 

 an internal perfecting tendency (Vitalism) in either the 

 origin of new characters or the origin of proportions. 

 (5) There are certain changes of length and breadth 

 proportion both in the shells of invertebrates and the 

 skulls of vertebrates which can not be explained by Or- 

 ganic. Selection. (6) There is very strong support in 

 fossil series for Selection incessantly acting on all char- 

 acters of survival or elimination value. 



The above six principles are those w^hich I have de- 

 rived from forty years of continuous observation; they 

 are actual modes of the mechanical evolution of new 

 species for which we have no theoretic explanation, un- 

 less it be that of Organic Selection in the single case 

 above noted. 



Summary of Opinions.— 1 may add as a matter of 

 personal opinion and hypothesis three points : first, that 

 we are as remote from adequate explanation of the na- 

 ture and causes of mechanical evolution of the hard parts 

 of animals as we were when Aristotle first speculated 

 on this subject three hundred years b.c. ; second, that the 

 chief outlook for experiment is in the domain of physics ; 

 third, that the explanation, if ever it is to be found, is to 

 be along the lines of four systems of energy (=Tetra- 

 plasy, Tetrakinesis, Osborn). which surround the origin 

 and development of every character in every organism; 

 fourth, I think it is possible that we may never fathom 

 all the causes of mechanical evolution or of the origin of 

 new mechanical characters, but shall have to remain con- 

 tent with observing the modes of mechanical evolution, 



