General Introduction 33 



progress to-day. In his earlier writings the influence of 

 Schleiden appears perhaps somewhat prominent, but Naegeli 

 soon showed himself a leader of thought. Among his con- 

 tributions to science may be mentioned his Zellenkerne, 

 Zellenbildung and Zellenwachstum, which was his first great 

 memoir ; in it \ve find the demonstration of the nucleus as 

 a structure occurring in the leading families of the Crypto- 

 gams as well as in the flowering plants, where it had been 

 seen by Robert Brown. His name may be associated 

 with that of von Mohl in the discovery of protoplasm, 

 though he called it ' Schleimschicht ' from its appearance 

 and apparent distribution. He carried out researches on 

 the Cryptogams, discovering the archegonia and antheridia 

 of Ferns, and making very important observations on 

 the Siphoneae and on the Florideae, in which group he 

 discovered the apical cell. It was perhaps by his theory of 

 the micellar structure of organized substances and of growth 

 by intussusception that he is best known to the younger 

 generation of botanists. It was a wonderful conception, 

 giving for the first time a theory in any way satisfactory 

 to the philosophic thinker. It received rapid recognition 

 and acceptance everywhere, and for some twenty years was 

 considered as the last possible word on the subject. 



Naegeli was a philosopher as well as an observer. He 

 took an active part in the controversy that followed the 

 appearance of the Origin of Species, opposing Darwin's 

 views for the most part and supporting those of Lamarck. 

 He held, in opposition to Darwin, that utility is a principle 

 which is quite inadequate to explain phylogeny. In 

 later years (1884) he published his views on evolution 

 in the Abstammungslehre, and showed therein a certain 

 approximation to the opinions of Darwin in postulating 

 a potentiality of complex differentiation of the soma. He 

 introduced the idea of a material basis for heredity in the 

 form of an ' idioplasm/ to which he attributed the trans- 



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