X PREFACE. 



The nearest approaches to a similar anticipation on the part of other 

 naturalists, which I have been able to find, refer to the number of toes only 

 and are of restricted application. Thus Kowalevsky remarks (" Monographie 

 der Gattung Anthracotherium, Palaeontographica," xxii, p. 1452) : " So we 

 can assume a tetradactyl foot as our point of departure, although it can 

 not have the least effect on the result in case the original ungulate foot 

 should have been pentadactv]. If I have set out with a tetradactyl foot 

 it is simply because I wish to adhere so far as possible to facts." This was 

 written August, 1873, but how soon thereafter it was printed I do not know. 

 I did not meet with it until at least a year after the publication of my paper 

 of March, 1874, cited. Secondly, Marsh, in writing on the genealogy of 

 the horses (" xVmerican Journal of Science and Arts," March, 1874, p. 257), 

 says: "A still older ancestor [of the horse], possibly in the Cretaceoui=, 

 doubtless had five toes on each foot, the typical number in mammals." My 

 paper was published during the same month as the above; but I communi- 

 cated the substance of the generalization in question to the Philadelphia 

 Academy the day it was read, November 18, 1873, which was published in 

 the "Proceedings of the Society, " January 18, 1874, p. 2. 



XVIII. Consciousness in Evolution. From the " Penn Monthly Maga- 

 zine," Philadelphia, July, 1875. 



In this paper the doctrine of intelligent selection is analyzed, and the 

 problem reduced to its essential — the relations of consciousness to matter. 

 The doctrine of the origin of reflex and automatic acts from conscious states, 

 or archaesthetism, is here first proposed. From the characters of proto- 

 plasm the inference is derived that that substance is not necessarily the only 

 one capable of supporting consciousness. The author is not aware of any 

 previous attempt to render these propositions probable. 



VIII. The Relation of Man to the Tertiaey Mammalia. From the 

 " Penn Monthly Magazine," December, 1875. Read before the American 

 Association for the Advancement of Science, at Detroit. 



The fact that the hard tissues, and probably the digestive system, of man, 

 are constructed on the type of the Mammalia of the early Eocene period 

 is here pointed out for the first time. 



III. The Theory of Evolution. Remarks made before the Academy 

 of Natural Sciences of Philadelphia, February 22, 1876, and published in the 

 "Proceedings of the Society," 1876, p. 15. 



These remarks exhibit the correspondence between the evolutionary 

 systems of Haeckel and of the writer, and combine them into a symmetrical 

 whole. 



XXI. The Origin of the Will. From the "Penn Monthly Magazine," 

 Philadelphia, June, 1877. 



In this paper the attempt is made to render the existence of freedom of 

 will probable by a process of argument, and also to demonstrate its exist- 

 ence by another kind of argument. As is well known, there are two op- 

 posed doctrines respecting this important question. One of these, which 

 has by far the larger number of adherent?, is that the human mind embraces 



