CHAPTER XX 



RETROSPECT AND PROSPECT. RECENT TENDEN- 

 CIES IN BIOLOGY 



When one views the progress of biology in retrospect, the 

 broad truth stands out that there has been a continuity of 

 development in biological thought and interpretation. The 

 new proceeds out of the old, but is genetically related to it. 

 A good illustration of this is seen in the modified sense in 

 which the theories of epigenesis and pre-formation have been 

 retained in the biological philosophy of the nineteenth cen- 

 tury. The same kind of question that divided the philos- 

 ophers of the seventeenth and eighteenth centuries has 

 remained to vex those of the nineteenth; and, although both 

 processes have assumed a different aspect in the light of ger- 

 minal continuity, the theorists of the last part of the nineteenth 

 century were divided in their outlook upon biological proc- 

 esses into those of the epigenetic school and those who are 

 persuaded of a pre-organization in the germinal elements of 

 organisms. Leading biological questions were warmly dis- 

 cussed from these different points of view. 



In its general character the progress of natural science 

 has been, and still is, a crusade against superstition; and it 

 may be remarked in passing that "the nature of superstition 

 consists in a gross misunderstanding of the causes of nat- 

 ural phenomena." The struggle has been more marked in 

 biology than in other departments of science because biology 

 involves the consideration of living organisms and undertakes 



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