ANIMAL KINGDOM. 321 



The third observation to be made is, that on leaving the 

 Acrita by means of the Tunicata, we immediately have the 

 nervous system directing all its energy to one principal gan- 

 glion, which is called the brain, and thus are led to the 

 very great intelligence of some Vertebrata; but on leaving 

 the Acrita by Zoanthus, the vital energy is apparently divided 

 among different ganglions, and we finally arrive at the very 

 great instinct of certain Annulosa. The complication and 

 perfection of structure in the animals we meet with in 

 this last path, neither increase so rapidly nor arrive to so 

 great a height as among those animals which possess a di- 

 stinct brain. The Mollusca and Radiata are equally di- 

 stant from the Infusoria, but the sluggish Mollusca are in 

 general endued with more proofs of life than the most or- 

 ganized of the Radiata. Perfection among the Annulosa 

 seems always tending to make the animal a complicated 

 machine, guided solely by an instinct implanted in it by its 

 Creator. Perfection in the Vertebrata seems to tend to 

 make the animal a free agent, and to render it more inde- 

 pendent of fatality. 



Fourthly, it can scarcely have escaped our notice, as some- 

 what remarkable, that each of the great groups appears to 

 be composed of five smaller ones ; for while it may be true 

 indeed, that, contenting myself with the ability to pass from 

 the Acephala to the Pteropoda, by means of the genus 

 Hyale, I have by no means determined this disposition 

 to hold good among the Mollusca; still, as it is equal]y 

 certain that this group of animals is as yet the least known, 

 it may be improper at present to conclude that it forms 

 any exception to the rule. It would even seem un- 

 questionable, that the Gasteropoda of Cuvier return into 

 themselves so as to form a circular group; but whether 



y 



