PREFACE. xi 



among its powers a freedom of will, or spontaneity in action. The other 

 view is, that there is no such power, but that the actions are merely the 

 necessary result of the strongest pressure of the strongest inducement or 

 motive. The doctrine of evolution is known to lend support to the latter 

 doctrine. In the present paper the attempt is made to prove that free will 

 is a new power which supervenes on the process of evolution. This is done 

 by assuming the existence of a class of acts for which the term altruistic is 

 retained, which, undoubtedly, would require freedom for their perform- 

 ance. The only question here is, whether there be any such class of acts as 

 are defined under the above name in this essay. If tliere be no such class 

 of acts, the demonstration based on it falls to the ground ; and the author 

 is xiot at present sure whether there be such a class of acts or not. 



The argument by which freedom of will is rendered probable is not 

 open to any serious objection, and rests on the necessity for action which 

 sometimes arises in cases where there is no experience or knowledge to serve 

 as a determining motive or power. These cases are supposed to involve 

 moral questions. The doctrine is then intermediate between the two oppos- 

 ing ones which have long divided the world of thought,* It permits of the 

 development of a free will in previously automatic beings, as a phenomenon 

 superposed on mental evolution. The argument demonstrates nothing more 

 tlian that freedom is possible; a conclusion which is, however, important, 

 since it shows that the position of the determinists is not impregnable, 



XII. The Relation of Animal Motion to Animal Evolution. From 

 " The American Naturalist," January, 1878. Read before the American 

 Association for the Advancement of Science, at Nashville, August, 1877. 



The effects of the actions of animals on their structure are considered, 

 as in previous papers, and especial attention is paid to the influence of ani- 

 mals in the changes they produce in their environment.t 



XI Y. The Origin of the Specialized Teeth of the Carnivoea. From 

 " The American Naturalist," March, 1879. 



The mechanical reasons for the changes in the dentition of carnivorous 

 mammals during geologic time are pointed out for the first time. 



VI. A Review of the Modern Doctrine of Evolution. From "The 

 American Naturalist," March and April, 1880. A lecture delivered before 

 the California Academy of Sciences, October 27, 1879. It is a general 

 synopsis of views presented in preceding papers. 



XY. On the Origin of the Foot-Structure of the Ungulates. 

 From " The American Naturalist," April, 1881. 



This essay embraces an explanation of the cause of the diminution of the 

 number of digits in the diplarthrous ungulate mammals ; of the reasons 

 why some are even- and some odd-toed ; and of the origin of some of the 



* This view is adopted by President Xoah Porter in one of his latest metaphysi- 

 cal works. 



f A synopsis of the relations of animals to their environment is given by Spen- 

 cer, " Principles of Biology," vol. i, p. 466. 



