524 NOTES TO BOOK XVII. 



time Sciences, Book ix. I have there (Chap, ii.) noticed 

 the successive Biological Hypotheses of the Mystical, the 

 latrochemical and latromathematical Schools, the Vital- 

 Fluid School, and the Psychical School. I have (Chap. 

 iii.,iv.,v.) examined several of the attempts which have been 

 made to analyze the Idea of Life, to classify Vital Func- 

 tions, and to form Ideas of Separate Vital Forces. I have 

 considered, in particular, the attempts to form a distinct 

 conception of Assimilation and Secretion, of Generation, 

 and of Voluntary Motion ; and I have (Chap, vi.) further 

 discussed the Idea of Final Causes as employed in Biology. 

 (x.) p. 495. The question of the Classification of Ani- 

 mals is discussed in the first of Prof. Owen^s Lectures on 

 the Invertebrate Animals (1843). Mr. Owen observes that 

 the arrangement of animals into Vertebrate and Invertebrate 

 which prevailed before Cuvier, was necessarily bad, inas- 

 much as no negative character in Zoology gives true natu- 

 ral groups. Hence the establishment of the sub-kingdoms, 

 Mollusca, Articulata, Radiata, as co-ordinate with Verte- 

 brata, according to the arrangement of the nervous system, 

 was a most important advance. But Mr. Owen has seen 

 reason to separate the Eadiata of Cuvier into two divi- 

 sions ; the Nematoneura, in which the nervous system can 

 be traced in a filamentary form (including Echinoderma, 

 Ciliolrachiata, Ccelelmintha, Rotifer a,) and the Acrita or 

 lowest division of the animal kingdom, including Acalepha, 

 Nudibrachiata, Sterelmintha, Polygastria. 



