RANK AND DEVELOPMENT OF ANIMALS. 179 



of incomplete investigations, have even become the foun- 

 dation of a system of philosophy of Nature which repre- 

 sents all animals as the different degrees of development 

 of a few primitive types. 1 These views have been too 

 generally circulated of late, in an anonymous work, en- 

 titled Vestiges of Creation, to require further mention 

 here. It has also been shown above (Sect. VIII.) that 

 animals do not form such a simple series as would result 

 from a successive development. There now, therefore, 

 remains only for us to show within what limits the natural 

 gradation which may be traced in the different types of 

 the animal kingdom, 2 corresponds to the changes they 

 undergo during their growth, having already considered 

 the relations which exist between these metamorphoses 

 and the successive appearance of animals upon earth, and 

 between the latter and the structural gradation or relative 

 standing of their living representatives. Our knowledge 

 of the complication of structure of all animals is suffi- 

 ciently advanced to enable us to select, almost at random, 

 our examples of the correspondence between the structural 

 gradation of animals and their embryonic growth, in all 

 those classes, whose embryological development has been 

 sufficiently investigated. Yet, in order to show more dis- 

 tinctly how closely ah 1 the leading features of the animal 

 kingdom are combined, whether we consider the compli- 

 cation of their structure, or their succession in time, or 

 their embryonic development, I shall refer by preference 

 to the same types which I have chosen before for the 

 illustration of the other relations. 



1 LAMARCK, q.a., p. 36. DE MAIL- LehrbuchderNatur-Philosophie,q.a., 



LET (Pseudon. TELLIAMED), Entre- p. 24. The Vestiges of Creation, etc. 



tiens d'un Philosophe indien avec un 2 See the works quoted from,p.!01- 



rnissionaire franais ; Amsterdam, 126, also MILNE-EDWARDS, q.a.,p. 169. 



1748, 2 vols. 8vo. OKEN (LoR ), THOMPSON, Crinoids, q. a. 



N 2 



