THEORIES OF ORGANIC EVOLUTION 



Baptiste de Lamarck. Possessed of the spirit of a poet 

 and philosopher, this great Frenchman had also the 

 widest range of technical knowledge, covering the en- 

 tire field of animate nature. The first half of his long 

 life was devoted chiefly to botany, in which he attained 

 high distinction. Then, just at the beginning of the 

 nineteenth century, he turned to zoology, in particular 

 to the lower forms of animal life. Studying these 

 lowly organisms, existing and fossil, he was more and 

 more impressed with the gradations of form every- 

 where to be seen ; the linking of diverse families through 

 intermediate ones; and in particular with the pre- 

 dominance of low types of life in the earlier geological 

 strata. Called upon constantly to classify the various 

 forms of life in the course of his systematic writings, 

 he found it more and more difficult to draw sharp lines 

 of demarcation, and at last the suspicion long harbored 

 grew into a settled conviction that there is really no 

 such thing as a species of organism in nature; that 

 4 'species" is a figment of the human imagination, 

 whereas in nature there are only individuals. 



That certain sets of individuals are more like one an- 

 other than like other sets is of course patent, but this 

 only means, said Lamarck, that these similar groups 

 have had comparatively recent common ancestors, while 

 dissimilar sets of beings are more remotely related in 

 consanguinity. But trace back the lines of descent far 

 enough, and all will culminate in one original stock. 

 All forms of life whatsoever are modified descendants 

 of an original organism. From lowest to highest, then , 

 there is but one race, one species, just as all the mul- 

 titudinous branches and twigs from one root are but 



VOL. IV. II 



