PERIOD V. 

 (1859 AND LATER) 



Period V. 



WE do not attempt to characterise our last period, nor 

 to describe its biological achievement. It seems better 

 to devote the whole of our scanty space to the scientific 

 careers of Darwin and Pasteur, in which so much past 

 effort culminated, and from which so much progress 

 was to spring. 



Darwin on the Origin of Species. 



Setting aside as superfluous and we might say 

 impossible, under our conditions of space, all attempt 

 to restate the evidence on which Darwin based his 

 great argument, we shall here try to show that the 

 Origin of Species shed a new light upon many biological 

 facts, combined many partial truths into one consistent 

 theory, and gave a great stimulus to further inquiry. 



i. Classification and Affinity. --^\\Q. sixteenth-century 

 herbalists and still earlier writers (see p. 17) recognised 

 a property of affinity, by which plants were associated 

 in natural groups. Bock (1546) tried to bring together 

 all plants which are related (verwandt) to one another, 

 but similarity of any kind was with him a proof of 

 affinity ; it did not shock him to place the dead nettles 

 next to the stinging nettles. L'Obel gave names to 

 several families of flowering plants which are still 

 admitted as natural. Ray spoke of the affinity 

 (cognatio) between plants, and his affinity was a thing 



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