The law that rules animal rules also vegetable nature: the phænogamous plants present a centre very nearly corresponding, in relative value, to vertebrates among animals; these, again, offer equal scope for subdivision; and the surrounding vegetations must be those at present termed cryptogamous, which vary as greatly among themselves as they collectively do from the more perfect and central ones: the various tribes of Fungi, Algæ, Filices, Musci, &c., possessing wonderfully varied forms and characters, and assuming every size from the gigantic fern of the tropical islands to that almost invisible Mucor, which seems, by its instantaneous appearance, to be for ever floating in the air, prepared to vegetate wherever it may chance to fall, and has often afforded arguments to those who deny the dictum of _omnia ex ovo_, and support that of spontaneous reproduction; thus ennobling these almost nonentities, by assigning to them properties which man might pine for in vain, and which cannot be the attributes of dust. The centre for each particular group will not always derive that mark of superiority from its size, or intelligence, or beauty, or complicated structure, but from a combination of these qualities, and more particularly from uniting in itself the principal and more decidedly distinguishing characters of the group of which it forms the nucleus, and the gradation will by no means be found to be regular, from the most perfect in the centre to the least perfect on the circumference of minor groups, although I imagine this relative position to obtain in the extremes: on the contrary, the approaches towards perfection or imperfection will be infinitely varied, presenting the most complete labyrinth of intricacies that imagination can conceive, yet all disposed with that beautiful and wonderful regularity which proclaims more loudly than words, that "the natural system is the plan of creation itself, the work of an ALL-WISE ALL-POWERFUL DEITY."[16] [16] Horæ Entomologicæ, preface, p. xiii. ON THE CLASSES OF INSECTA.