268 



Chapter IV. 



ARTICULATA. 



§ 1 . Articulated Animals in general. 



From the Cephalopoda, the transition is easy to 

 the lowest order of vertebrated animals. But 

 previously to pursuing the analogies which con- 

 nect these two divisions of the animal kingdom, 

 we have to pass in review a very extensive series 

 of animal forms, constructed upon a peculiar 

 system, and occupying, as well as the Mollusca, 

 a place intermediate between Zoophytes and the 

 more highly organized classes. 



We have seen that even in those Zoophytes 

 which are distinguished from the rest by a more 

 elaborate conformation of organs, the powers of 

 progressive motion are always extremely limited. 

 Nor are the Mollusca in general more highly 

 favoured with respect to the degree in which 

 they enjoy this faculty. But the greater number 

 of the animals composing the series we are now 

 to examine are provided with a complete appa- 

 ratus for motion, and endowed with extensive 

 capacities for using and applying it in various 

 ways. While nature has preserved in the con- 

 struction of their vital organs the simplicity which 

 marks the primitive modes of orga^iization, and 



