ASPECTS OF KINETIC EVOLUTION 255 



organisms might be carried along in an ever-upward direction. 

 Some species have gone forward or upward, but for each of the 

 groups which has been able to perpetuate itself by continuing 

 upward there have been hundreds and thousands which have 

 not continued in lines of effective progress, but have turned 

 aside and have been extinguished. This is as true of man and 

 of human societies as of species. They do not tend to go 

 upward but they do tend to change and these changes have 

 carried a few upward to higher levels, where new planes of 

 development and expansion were possible, but where the prob- 

 abilities of still further steps were as doubtful as before, and as 

 truly dependent upon correct, if unconscious choice. One view 

 is teleological, the other purely causational. 



The phenomenon of degeneration, the reduction or elimination 

 of unused parts or organs, has led to the placing of undue 

 emphasis upon the utilitarian aspect of evolution. Darwin 

 attempted to connect the deficient size and strength of the unused 

 organs of the individual with their reduction in the species by 

 means of his theory of pangenesis which assumed that all parts 

 of the body contribute to the reproductive cells. Degeneration 

 was made a converse of natural selection ; the reduction was 

 believed to appear first in the adult, and then the negative 

 acquired character was transmitted to the next generation. 

 Many characters of adult organisms consist in part of a genetic 

 or hereditary contribution, which might be called a qualitative 

 element, to which is added during growth a quantitative reaction 

 to more or less favorable conditions, depending not only upon 

 external circumstances but also upon the perfection and effi- 

 ciency of the remainder of the organism. Disuse undoubtedly 

 affects the quantitative side of the development of voluntary 

 muscles and other analogous organs, but it is not easy to under- 

 stand how a progressive reduction could be brought about on 

 Darwin's hypothesis. 



After the elimination of the quantitative element due to use, a 

 state of stability might be expected to ensue, unless there be 

 predicated in addition a principle of organic economy tending 

 to the gradual and continued elimination of useless characters 

 and organs. In other words, the effect of pangenesis acting 



