472 The American Naturalist. [June, 



tion is concerned with two distinct fields of human inquiry/' he dis- 

 tinguishes them as follows : 



" On the one h&nd, evolution is the name for the natural order of un- 

 folding of the character* <>/ <,,r/anit on the earth ; 

 on the other hand, evolution is the name for our conception of the mode 

 of operation of the fundamental > nergij of the u„ie, rst . Thus it will be 

 seen that the notion of God is as intimately involved in a discussion of 

 evolution as is the notion of an organism." He sees in evolution the 

 mode of creation of organic beings, a process that has been more or less 

 continuous throughout geologic ages. " It is this continuation of the 

 process of phenomenalizing that distinguishes the mode of creation in 

 the organic realm from that in the lower realm of inorganic matter. 

 Whatever is characteristic of organisms was not created at once, but 

 has been unfolded by degrees, and there is no reason for supposing that 

 the process is not still going on. Such expressions as ' effort/ 'growth 

 force,' ' reactions,' etc., used in describing the phenomena of evolution, 

 all express the notion of the preexistence of some unphenomenal prop- 

 erty, or power, or potency, which constitutes the cause of the particu- 

 lar characters which are acquired by organisms in the process of their 

 evolution." 



The tendency of organisms to vary is designated by the author as 

 primarily a force acting from within, to which he gives the name " in- 

 trinsic evolution." Differentiation of form and function are expres- 

 sions of vitality, but these are modified by conditions of environment 

 and natural selection. 



A summary of the leading points in the work are thus given : 



" The great facts attested by geology are that the grander and more 

 radical divergences of structure were earliest attained ; that, as time 

 advanced, in each Hue intrinsic evolution has been confined to the ac- 

 quirement of less and less important characters ; such facts emphasize 

 with overwhelming force the conclusion that the march of the evolu- 

 tion has been the expression of a general law of organic nature, in which 

 events haveoccured in regular order, with a beginning, a normal order 

 of succession, a limit to each stage, and in which the whole organic 

 kingdom has been mutually correlated." 



This book will prove instructive to the general reader, both on ac- 

 count of its facts and generalizations. The author, as a distinguish* d 

 specialist in paleontology presents facts in an authoritative way, so that 

 the reader may feel safe in his premises. The inferences made are 

 obvious, so that while there is little exposition of efficient causes of 

 evohltbo in the scientific sense, one can agree with the general conclu- 



