446 



SCIENCE. 



[N. S. Vol. III. No. 



immense antiquity of geological time " (p. 3). 

 " The history of organisms which we particu- 

 larly trace in the study of fossils is not the his- 

 tory of imperfect organisms struggling toward 

 perfection, but it is the history for each age and 

 epoch of the perfected adjustment of the organ- 

 isms of the time to the particular conditions of 

 environment in which they lived. They did not 

 die before their time, overcome by the mythical 

 iittest who are said to survive in the struggle. 

 They were the fittest and died natural deaths, 

 having provided, before they gave up the strug- 

 gle for their progeny, to succeed them. The 

 hard parts record the history of adults which 

 had endured the struggle, and thus represent 

 the royal line of succession for the geological 

 ages " (p. 81). 



The book opens with a discussion of the his- 

 tory of organisms and its geological aspect. 

 The second chapter gives an excellent and in- 

 teresting summary of the history of geology, 

 which is followed by a discussion of the geolog- 

 ical time-scale, and of the nature, nomenclature 

 and fossil contents of stratified rocks, geograph- 

 ical distribution, the nature and origin of spe- 

 cies, the acquirement of characters, intrinsic 

 and extrinsic, their plasticity and permanency. 

 The rate of morphological diiferentiation and 

 progressive modification are considered at length 

 and illustrated by the history of selected types. 

 The final chapters treat of the laws of evolution 

 as illustrated by the geologic history of organ- 

 isms and the philosophical conclusions drawn 

 therefrom. 



The author concludes that "the Animal King- 

 dom is divisible into a number of definite groups 

 marked by definite organization, all the grander 

 features of which were outlined in the Cambrian 

 age, and the large majority of all the differ- 

 entiations of even ordinal rank had been ac- 

 complished in the first quarter of the recorded 

 history of organisms," hence the laws of evolu- 

 tional history must be read in terms of the 

 minor groups. As emphasized by fossils these 

 laws include an orderly succession of increasing 

 differentiations in organic structure which we 

 call evolution ; certain parts of each organism 

 exhibit the progress of evolution more rapidly 

 than other parts, the characters of least struc- 

 tural importance showing the most constant 



and steady but slow differentiation, while the 

 characteristics of higher rank are relatively 

 more rapid in their initial development and sub- 

 sequently very constant in each successive gen- 

 eration. These two tendencies are expressive 

 of the two fundamental laws of heredity and 

 variability, and the process of evolution is the 

 combined result of their interaction. The mode 

 of evolution consists in the acquirement of new 

 chaj-acters by variation and in the acceleration 

 pr retardation of development of characters 

 already required. The causes of evolution are 

 extrinsic or intrinsic, the former being of the 

 nature of an adjustment to the environment 

 direct or selective; the latter " acts previous to 

 the individual birth and seems to be at the 

 foundation of variability. The mode and man- 

 ner of expression of this kind of evolution are 

 more difiicult to define than in the case of ex- 

 trinsic evolution, but the facts of paleontology 

 clearly indicate that such a cause exists prior 

 to the morphological appearance of each indi- 

 vidual and species" (pp. 369-70). 



"The great facts attested by geology," ac- 

 cording to Prof. Williams, ' 'are that the grander 

 and more radical divergencies of structure were 

 earliest attained ; that, as time has advanced, 

 in each line intrinsic evolution has been con- 

 fined to the acquirement of less and less im- 

 portant characters ; such facts emphasize with 

 overwhelming force the conclusion that the 

 march of the evolution has been the expression 

 of a general law of organic nature in which 

 events have occurred 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. * * * 

 So were we to lengthen out the gyration of or- 

 ganic plastidules or biophores, a million million 

 years, continuously holding on to their original 

 powers and potencies for all that time, we are 

 not relieved in the least from the logical neces- 

 sity of endowing them at the outset with the 

 real directive energy which phenomenally ex- 

 presses itself for the first time when the finally 

 adjusted organism appears. And the increment 

 to organic structure expressed by their final 

 bursting into morphological reality after trav- 

 elling unobserved but potential through the 

 organic matter of countless generations is as 



