524 NOTES TO BOOK XVII. 



five 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.) farther 

 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 Radiata of Cuvier into two divi- 

 sions ; the Nematoneura, in which the nervous system can 

 be traced in a filamentary form (including Echinoderma, 

 Ciliobrachiata, Ccelelmintha, Rotifera,) and the Acrita or 

 lowest division of the animal kingdom, including Acalepha, 

 Nudibrachiata, Sterelmintha, Polygastria. 



