244 ESSAY ON CLASSIFICATION 



but forming so many connecting or osculant circles.^o The number, therefore, 

 as many erroneously suppose, is not five, but ten. This is quite obvious; and our 

 opinion on this point is confirmed by the author himself, in the following pas- 

 sage, when alluding to his remarks upon the whole: "The foregoing observa- 

 tions, I am well aware, are far from accurate, but they are sufficient to prove 

 that there are five great circular groups in the animal kingdom, each of which 

 possesses a peculiar structure; and that these, when connected by means of five 

 smaller osculant groups, compose the whole province of Zoology." Now these 

 smaller osculant groups are to be viewed as circles, for, as it is elsewhere stated, 

 "every natural group is a circle, more or less complete." This, in fact, is the 

 third general principle of Mr. MacLeay's system, and he has exemplified his 

 meaning of a natural group in the above diagram, where all animals are ar- 

 ranged under five large groups or circles, and five smaller ones. Let us take one 

 of these groups, the Vertebrata: does that form a circle of itself? Yes; because 

 it is intimated that the Reptiles (Reptilia) pass into the Birds (Aves), these again 

 into the Quadrupeds (Mammalia). Quadrupeds unite with the Fishes (Pisces) 

 these latter with the amphibious Reptiles, and the Frogs bring us back again 

 to tlie Reptiles, the point from whence we started. Thus, the series of the verte- 

 brated group is marked out and shown to be circular; therefore, it is a natural 

 group. This is an instance where the circular series can be traced. We now turn 

 to one where the series is imperfect, but where there is a decided tendency to a 

 circle: this is the Mollusca. Upon this group our author says, "I have by no 

 means determined the circular disposition to hold good among the Mollusca; 

 still, as it is equally 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 unquestionable that the Gasteropoda of Cuvier return 

 into themselves, so as to form a circular group; but whether the Acephala form 

 one or two such, is by no means accurately ascertained, though enough is known 

 of the Mollusca to incline us to suspect that they are no less subjected, in gen- 

 eral, to a circular disposition than the four other great groups." This, therefore, 

 our author considers as one of those groups which, without actually forming a 

 circle, yet evinces a disposition to do so; and it is therefore presumed to be a 

 natural group. But, to illustrate this principle farther, let us return to the 

 circle of Vertebrata. This, as we see by the diagram, contains five minor groups, 

 or circles, each of which is again resolvable into five others, regulated precisely 

 in the same way. The class Aves, for example, is first divided into rapacious 

 birds (Raptores), perching birds (Insessores), gallinaceous birds (Rasores), wad- 

 ing birds (Grallatores), and swimming birds (Natatores); and the proof of this 

 class being a natural group is in all these divisions blending into each other at 

 their confines and forming a circle. In this manner we proceed, beginning with 

 the higher groups, and descending to the lower, until at length we descend to 

 genera, properly so called, and reach, at last, the species; every group, whether 

 large or small, forming a circle of its own. Thus there are circles within circles, 

 "wheels within wheels," — an infinite number of complicated relations; but all 

 regulated by one simple and uniform principle, — that is, the circularity of 

 every group. 



^ In the original diagram, as in that above, these five smaller circles are not repre- 

 sented graphically, but merely indicated by the names arranged like rays between the 

 five large circles. 



