130 KARL ERNST VON BAER 



in a sense embryos of Amphibia (p. 547). But this manner 

 of viewing things is none the less vicious, "for this 

 reason . . . that it considers only one or two points and 

 neglects all the others " (p. 548), and is directly contrary to 

 common sense. There is never a recapitulation of total 

 organisations, only at the most of single organs. 



It will be remembered that Cuvier opposed and 

 demolished the theory of the lichcllc des ctrcs, not only 

 by showing that there were in Nature four entirely different 

 plans of animal structure, but also by demonstrating that 

 even the animals of each single Embranchement could not 

 readily be arranged in one series, that a serial arrangement 

 was really valid only for their separate organs. Von Baer 

 also held that there are four distinct types of structure ; 

 he, too, combated the idea of gradation within the limits of 

 the type. Jn so far as species represent successive stages 

 in the development, the Ausbildung, of the type, so far can 

 the idea of a scale of beings be applied. But the members 

 of a type follow not one line of evolution but several 

 diverging lines, in direct adaptation to different environ- 

 mental conditions, so that a serial arrangement of them 

 is not as a rule possible. It may be possible to establish 

 a serial arrangement of single organs from the simplest 

 to the most complex. But each organ or organ-system 

 will require a different serial arrangement, for the different 

 systems vary on different lines and an animal may be highly 

 developed in respect of one system and little developed in 

 respect of all the others. Man, for instance, is the highest 

 animal only in respect of his nervous system. The idea 

 of the scale of beings has therefore only a very limited 

 application even within the limits of the type. .Applied to 

 the whole animal kingdom it becomes merely absurd. 



Another point of resemblance between Cuvier and von 

 Baer was that Cuvier, though essentially a student <>f adult 

 structure, did recognise the importance of embryology; 

 following up some observations of Dutrochet he studied the 

 f-i-tal membrane of mammals and trird to establish their 

 homologies. 1 And in his criticism of the vertebral theory of 

 the skull he advanced as an argument against the basi- 



/.r. d'Hist. t\<it., iii., pp. 9^-119, 1817. 



