18641869] NAG ELI 273 



be discussed at full length or not at all. He makes a mistake Letter 193 

 in supposing that I say that useful characters are always 

 constant. His view about distinct species converging and 

 acquiring the same identical structure is by implication 

 answered in the discussion which I have given on the 

 endless diversity of means for gaining the same end. 



The most important point, as it seems to me, in the 

 pamphlet is that on the morphological characters of plants, 

 and I find I could not answer this without going into much 

 detail. 



The answer would be, as it seems to me, that important 

 morphological characters, such as the position of the ovules 

 and the relative position of the stamens to the ovarium 

 (hypogynous, perigynous, etc.) are sometimes variable in the 

 same species, as I incidentally mention when treating of the 

 ray-florets in the Composite and Umbelliferae ; and I do 

 not see how Nageli could maintain that differences in such 

 characters prove an inherent tendency towards perfection. I 

 see that I have forgotten to say that you have my fullest 

 consent to append any discussion which you may think 

 fit to the new edition. As for myself I cannot believe in 

 spontaneous generation, and though I expect that at some 

 future time the principle of life will be rendered intelligible, 

 at present it seems to me beyond the confines of science. 



Kilchberg, near Zurich. He graduated at Ziirich with a dissertation on 

 the Swiss species of Cirsium. At Jena he came under the influence of 

 Schleiden, who taught him microscopic work. He married in 1845, and 

 on his wedding journey in England, collected seaweeds for Die neueren 

 Algen-systeme. He was called as Professor to Freiburg im Breisgau in 

 1852 ; and to Munich in 1857, where he remained until his death on 

 May loth, 1891. In the Zeitschrift fur ivtss. Botanik, 1844-46, edited 

 by Nageli and Schleiden, and of which only a single volume appeared. 

 Nageli insists on the only sound basis for classification being " develop- 

 ment as a whole." The Entstehung und Be griff (\^,6^] was his first real 

 evolutionary paper. He believed in a tendency of organisms to vary 

 towards perfection. His idea was that the causes of variability are 

 internal to the organism : see his work, Ueber den Einfluss ausserer 

 Verhaltnisse auf die Varietatenbildiing. Among his other writings are 

 the Theorie der Bastardbildimg, 1866, and Die Mecha?iisch-physiologische 

 Theorie der Abstammimgslehre^ 1884. The chief idea of the latter book 

 is the existence of Idioplasm, a part of protoplasm serving for hereditary 

 transmission. (From Dr. D. H. Scott's article in Nature, Oct. I5th, 

 1891, p. 580.) 



18 



