2l6 COOK 



has become increasingly obvious that many of the characters 

 which differentiate related species and genera are quite lacking 

 in environmental utility, and probably always have been. 

 Many characters which are now useful could have had little or 

 no utility at the time of their inception unless they appeared 

 suddenly in a highly developed state, as suggested by the now 

 popular doctrine of mutation. 



The kinetic theory enables us to understand that during the 

 earlier period, while a character has only an organic utility, it 

 nevertheless tends to be preserved and to become more and 

 more accentuated, in accordance with the principle of kinesis 

 or prepotency of new variations and recently acquired characters, 

 just as though the species were actively concerned to test the 

 environmental possibilities of each of the new characters it may 

 be able to develop. In this view there is no period in which 

 the new character is entirely useless. Its continued develop- 

 ment is normal and advantageous on the ground of organic 

 utility, unless it happens to encounter some environmental 

 obstacle which forbids further advance, or unless an excessive 

 development is attained which weakens or unbalances the 

 organism. 



In comparatively rare cases an acute natural selection may 

 intervene and establish a standard for the species by eliminating 

 all individuals which do not have a certain character developed 

 to a required degree. If only one course of evolution remains 

 open, progress in this direction may be greatly accelerated, for 

 as the normal diversity of descent is eliminated the prepotency 

 of the remaining variations appears to increase. This is not 

 because the environment is hastening the perfection of a new 

 form of fitness, but because it is of the nature of species to 

 change, and to continue in the direction of further development 

 of the characters already possessed. 



As far as environmental causes are concerned, there appears 

 to be complete fortuity in the appearance and development of 

 characters, except as selective specialization intervenes. This 

 may occur, of course, at any time in the development of the 

 character, and may lend it an environmental significance not 

 possessed before, and perhaps not continued except for a limited 



