RANK OF CIRCULAR GROUPS. 343 



groups that have been detected in the animal kingdom, 

 whose affinities proceed in a circle, are nine, and they 

 are thus designated, commencing from the highest and 

 descending to the lowest : — 1. Kingdom, 2. Sub-king- 

 dom, 3. Class, 4. Order, 5. Tribe, 6. Family, 7- Sub- 

 family, 8. Genus, 9- Sub-genus. 



(423.) It has been long customary, not only in 

 science, but in ordinary parlance, to designate the three 

 great divisions of ponderable matter as the animal, the 

 vegetable, and the mineral kingdoms of nature ; and, 

 although it is not yet ascertained in what precise manner 

 the vegetable, or, perhaps, also, the mineral kingdom *, 

 describe their own circles, yet it is sufficient for our 

 present purpose that the animal kingdom forms a cir- 

 cular group, comprehending all beings which usually pass 

 under that name, and all the ranks of groups we are 

 about to describe. A kingdom, therefore, is the first 

 and greatest circle ; and a sub-kingdom, as its name im- 

 plies, is one of the primary divisions of the animal 

 kingdom : of these, according to Mr. MacLeay, there 

 are five, namely, 1. the Vertebrata, or vertebrated 

 animals, having an internal bony skeleton ; 2. the An- 

 NULosA, or annulose animals, as insects, where the body 

 and legs are jointed, and the hardest parts are outside ; 

 3. THE Radiata, or radiated animals, which, hke the 

 star-fish, have the mouth in the middle; 4. the Acrita, 

 or the animalcules; 5. the Mollusca, or shell-fish, 

 whose nervous system is composed of several scattered 

 masses or ganglions, united by nervous threads, and 

 whose soft bodies are generally protected by a shell. The 

 three last groups, the Mollusca, the Acrita, and the Ra- 

 diata, are the aberrant divisions or sub-kingdoms of the 

 animal kingdom ; which, if our conclusions be correct, 

 form a circle more or less complete among themselves. 

 We shall not, however, in this part of our work, pro- 

 ceed to alter the definite divisions from five to three, it 

 being much better that the first of these numbers 



• See Northern Zoology, ii. Preface, p. liv. 

 z 4 



