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CHAPTER XI. 



Functions and Instincts. Worms. 



WE are now at length, after long wanderings, 

 arrived, if I may so speak, at the limits of the 

 Molluscan territory, and, having visited the 

 capital, seem now to be upon the confines of the 

 higher hemisphere of the animal kingdom, the 

 inhabitants of which are distinguished by having 

 their whole frame built upon a vertebral column, 

 inclosing a medullary chord, and terminating, at 

 its upper extremity, in a skull containing a de- 

 veloped brain. 



But though we seem arrived at the confines of 

 this higher order of animals, there are still many, 

 and some superior to the most perfect of the 

 Molluscans, in the entirety of their nervous 

 system, and the habits and instincts which they 

 manifest, to which we have not yet paid the 

 attention that they merit. These animals are 

 particularly distinguished from the preceding 

 Classes, by the appearance, or actual existence of 

 segments or joints in their bodies, especially in 

 their legs, of what may be called an annular 

 structure. They are divided into two great 

 tribes, which, from this circumstance, have been 



