ON TIIK GENKTIC VIKW OF NATURE. 



317 



different in their mental attitude, the two men agreed 

 in lookinii for tlie advancement of natural science in 

 an understamling ol' the simpler, unspecified, and un- 

 dittl'rentiateil forms or stages of existence out of which 

 they conceived the more complex to have grown or de- 

 veloped by a process of specialisation or differentiation. 

 Many other naturalists and philosophers contributed, 

 partly independently, partly through the influence of 

 Lamarck's systematic and von Baer's endiryological 

 labours, to elaborate the same ^•iew and strengthen the 

 same tendency of thought and research. Nor were 

 there wanting suggestions as to the ultimate philo- 

 sophical drift of the line of reasoning. It is doubtful 

 whether these speculations, like those of Oken in his 

 ' Physio-philosophy,' did not retard rather than promote 

 the acceptance of the genetic view by scientific thinkers : ^ 



' On tlie position of Uoetlie and 

 Oken in the history of the genetic 

 view, see Carus, ' Geschichte der 

 Zoologie,' p. 723 ; von Baer, 

 ' Reden und wissenscliaftliche Ab- 

 handluiigen,' Bd. II. p. '2.')8, «kc. 

 Both consider Lamarck as the real 

 originator of a scientific theory of 

 Descent. Von Baer gives an amus- 

 ing account of the extent to which, 

 as early as 18-29, actual genealogical 

 trees were given in Jacob Kaup's 

 ' Skizziitc Kntwickelungsgeschichte 

 und naturliches System der Eur- 

 opaeischen Thierwelt.' Von Baer 

 sums up his historical account in 

 the following words (p. 26-1): "In 

 general 1 believe that at that time, 

 when the succession of different 

 animals and plants in the history of 

 the earth — and generally from im- 

 perfect to more perfect organisms 

 — occupied the thoughts of natural- 

 ists, and when, at the same time, 

 tlie study of development of single 



I organisms had taken a new start, 

 I the notion of their 'I'ransformation 

 I was pretty generally accepted.'" 

 The view expiessed here by von 

 Baer would probably have to 

 be limited to German naturalists at 

 that date. It must, however, bo ad- 

 mitted that the fairest exposition 

 and criticism of the arguments of 

 Lamarck at that earlj* date is prob- 

 abh' to be found in Lyell's ' Prin- 

 ciples of Geology' (vol. ii. Bk. III. 

 chap. i. to iv. ) He there also con- 

 siders the arguments derived from 

 embryology as contained in the re- 

 searches of Thiedemann, confirmed 

 by Serres ('Anatomic Compareo du 

 Cerveau,' 1824), and comes linally 

 to the result that— 1. "There is a 

 capacity in all species to accommo- 

 date them-selves." 2. " Tliat the 

 mutations thus superinduced are 

 governed by constant laws." 3. 

 That " some acquired jieculiarities 

 of form, structure, and instinct are 



