378 NATURAL SCIENCE [December 



as involving the continuous adjustment of internal relations to 

 external relations, is developed. To this part a new chapter on the 

 Dynamic Element in Life is added. 



After an indication of the scope of biology, the inductions of 

 the science are considered in Part II. Generalizations as to 

 growth, development, adaptation, genesis, heredity, and variation, 

 are formulated and illustrated ; the classification and distribution of 

 organisms are considered, and the foundations are thus laid for the 

 erection of an aetiological superstructure. The special- creation 

 hypothesis is contrasted with that of evolution ; the arguments for 

 the latter are marshalled ; and the causes of evolution discussed. 

 Internal and external factors are distinguished ; and the phenomena 

 are explained as due to the joint action of (1) direct equilibration 

 through the inheritance of acquired modifications, and (2) indirect 

 equilibration through the survival of the fittest in the process 

 termed by Darwin ' natural selection.' A concluding chapter 

 on Eecent Criticisms and Hypotheses, in which any inherent 

 tendency to evolution along predetermined lines is rejected, brings 

 the volume to a conclusion, save for Appendices, amongst which 

 are the Contemporary Review articles on the Inadequacy of 

 Natural Selection. 



In the additional matter of the present edition Mr Herbert 

 Spencer would probably lay most stress on the chapter which deals 

 with the Dynamic Element in Life, and on the arguments in favour 

 of direct equilibration through the inheritance of acquired modifica- 

 tions. While other additions, such as those on protoplasm, on 

 metabolism, on nuclear changes, on embryological development, and 

 on classification, serve mainly (for there are original suggestions) to 

 bring the work into line with modern biological conclusions, the 

 supplementary discussion of the Dynamic Element in Life is in 

 touch with the author's distinctive philosophical tenets, and the 

 arguments for direct equilibration are adduced in support of 

 biological conclusions which Mr Spencer regards as of extreme 

 importance. It seems desirable therefore to direct attention 

 specially to these points. 



After leading up to a conception of Life as the definite com- 

 bination of heterogeneous changes, both simultaneous and successive, 

 in correspondence with external co-existences and sequences, and 

 after urging that the degree of life varies as the degree of corre- 

 spondence, Mr Spencer briefly indicates certain vital processes which 

 remain outside the conception as thus formulated, and contends 

 that all cases " exhibit that principle of activity which constitutes 

 the essential element in the conception of life." This he terms the 

 dynamic element in life ; and he asks whether it is inherent in 

 organic matter or is something superadded. The notion of a super- 



