XXXV 



their " swelling-up " and their behaviour with polarised light, Nageli 

 ^arrived at the conclusion that the micellae are biaxial crystals, and 

 assigned to them as a probable form that of parallelopipedal prisms 

 with rectangular or rhomboid bases. On this theory of their struc- 

 ture, the growth by intussusception of cell- walls and starch-grains 

 would consist essentially in the stretching of the growing layer so as 

 to widely separate the existing micelloe, and in the intercalation of 

 new micellae into the intervening watery areas. 



Brilliant as was this attempt to give a purely physical explanation 

 of certain biological phenomena, and helpful as it undoubtedly was 

 for a time, it must now be confessed that it was inadequate, and that 

 it is to no small extent responsible for the tendency to regard plants 

 more as inanimate objects than as living organisms, which for many 

 subsequent years impeded rather than assisted the advance of know- 

 ledge as to the mechanism, and physiology of the growth and other 

 movements of plants. 



Incomplete as this notice is, and indeed must be, it would be alto- 

 gether inadequate were it not to include some account of Nageli's 

 attitude with regard to evolution, a subject upon which he was 

 peculiarly qualified, both by his philosophical habit of mind and his 

 observations as a naturalist, to express a weighty opinion. Through- 

 out his life he was an enthusiastic field-botanist, and acquired a special 

 familiarity with the remarkable phenomena of distribution presented 

 by the flora of his native Alps. With the view of giving precision to 

 his field-observations, he devoted particular attention to the large and 

 highly variable genus Hieracium, the thoroughness of his study being 

 attested by a number of papers on the genus in the ' Botanische 

 Mittheilungen,' and by a monograph ' Die Hieracien Mittel-Europas,' 

 prepared in conjunction with Peter, of which the first volume 

 (" Piloselloiden ") was published in 1885, whilst the second (" Archier- 

 acien ") was not completed at the time of his death. 



The first definite statement of Nageli's views on evolution appears 

 in an address delivered before the Bavarian Academy, on March 28, 

 1865, entitled " Entstehung und Begriff der naturhistorischen Art," 

 which is to a large extent a criticism of the ' Origin of Species.' 

 Beginning, with characteristic completeness, at the origin of living 

 organisms, Nageli emphasises the importance of Lamarck's assump" 

 tion that the simplest organisms were, and are continually, formed 

 by spontaneous generation. Going to the consideration of Darwin's 

 theory of evolution by natural selection, Nageli regards it as being 

 based essentially on the principle of utility, "die Nutzlichkeits- 

 theorie ist der Darwinismus " — a principle which he considers to be 

 quite inadequate to explain the facts of the phylogeny of either plants 

 or animals. Darwin's theory, which involves the assumption that 

 variation takes place indeterminately in all directions, both higher 



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