308 



SCIENTIFIC THOUGHT. 



18. 



Phylotaxy 

 and phylo- 

 genesis. 



upon this order as systematic only, and ideal ; l he thinks 

 merely of arrangement or "taxonomy." We may say 

 that he deals with phylotaxy (called at that time tax- 

 onomy), not with phylogenesis. He conceives that onto- 

 genesis, the historical development of the individual 

 thing, throws light on the " mutual relations of organ- 

 ised bodies " ; 2 he wishes to make ontogenesis helpful 

 in taxonomy or in phylotaxy. This term did not then 

 exist, but it is useful in order to enable us to under- 

 stand the change which came over natural science when 

 the attempts at phylotaxy were succeeded by the schemes 

 of phylogenesis, when reasons were established for taking 

 in real earnest the idea then fancifully 3 put forward that 

 the natural order of living beings represented the order 

 in which they had developed out of each other in time. 

 These reasons did not at that time exist. 



A suggestion in this direction had indeed been thrown 

 out, and an elaborate theory had been published about 



1 In his later writings von Baer 

 notes especially the difference be- 

 tween a purely ideal and a genetic 

 or genealogical relationship. See 

 ' Reden, &c.,' vol. ii. p. 386 (2nd ed.) 



2 'Entwickelungsgeschichte' 

 (1828), p. 231; transl., p. 221. 



3 In a later publication of von 

 Baer's (see 'Reden, &c.,' 2 Theil, 

 No. V., " Ueber Darwin's Lehre") 

 the aged author tries to define more 

 exactly the part which his early 

 writings played in the gradual 

 establishment of a genetic concep- 

 tion of nature. If Haller arrived 

 ultimately at the dictum "es gibt 

 kein Werden, " we may say that von 

 Baer as emphatically asserted the 

 opposite, that "es gibt kein Sein." 

 In Baer we have progressed from the 

 study of the " esse " (fixed forms) to 



that of the "fieri" (processes of 

 change and development). See the 

 expositions in the introduction to 

 the article on Darwin. He there 

 also mentions Meckel and Oken as 

 the two principal exponents of the 

 extreme view then put forward and 

 opposed by himself, that the human 

 being in its development passes 

 through the different higher forms 

 of the animal creation, and he 

 maintains that Johannes Miiller, 

 who had in the first edition of his 

 1 Physiology ' accepted this view, 

 struck it out in the second. He 

 also refers to a passage in a Memoir 

 of 1859, published just before the 

 appearance of the ' Origin of 

 Species,' in which he maintains his 

 belief " that formerly organic forms 

 were less rigid." 



