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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