THE "GENEEAL MORPHOLOGY" 225 



holding scientific congresses. Oken had been 

 constantly occupied with embryology, the science 

 of the development of the individual organism. 

 He was at all events acquainted with all that was 

 known at the time on the subject. I open an old 

 volume, wretchedly printed on blotting-paper, of 

 Oken's General Natural History for all Headers 

 (1833), and turn to a passage in the fourth volume 

 (the first to be issued) on page 470. 



We read that the caterpillar of the butterfly 

 resembles the animal form at a stage of develop- 

 ment that lies below the insect — the worm. Oken 

 says: ''There is no doubt that we have here a 

 striking resemblance, and one that justifies us 

 in thinking that the development in the ovum is 

 merely a repetition of the story of the creation of 

 the animal groups." Oken was quite aware that 

 the chick in the egg had gill-slits like the fish. 

 He bases his idea on that fact. He was very close 

 indeed to the theory that Haeckel has so wonder- 

 fully elaborated. However, he was greeted with 

 laughter. His theory was treated as an absurdity 

 from 1833 to 1866. It cannot be denied that he 

 was himself partly to blame for this. Oken made 

 two serious mistakes. On both points Haeckel is 

 perfectly clear and sound. Moreover, the theory 

 of natural evolution that made it possible for us to 

 speak of *' ancestors *' was still a Cinderella in the 

 days of Oken. No sooner was it rehabilitated than 

 the principle of the old theory of embryonic forms 

 returned once more. 

 Darwin himself at once appealed to it, but it 



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