The diversity of form and structure in the group of land Carnivora is very great. We find, as in the groups we have considered previously, many different kinds or _species_, amongst which are creatures so different as the great and powerful Lion and the small and insignificant Weasel, the active Tiger and Jaguar, and the lazy Glutton. These species, as very little observation shows us, naturally fall into certain larger groups or _genera_, having important characteristics in common; for instance, the Lion, Tiger, Leopard, Jaguar, Lynx, and all the small Cats, are so much like one another, and so different from all other animals, as to be put in the one genus _Felis_, which is distinguished by having retractile claws, and by being quite devoid of true grinding teeth. Again, the Dog and Wolf have so many points in common, that they are placed in the single genus _Canis_, the Dog being called _Canis familiaris_, the Wolf _Canis lupus_. If a number of genera are found to agree pretty closely with one another in essential matters, they are grouped into a _family_; thus we have the family _Mustelidæ_, which includes not only the Weasel (_Mustela_), but a number of other genera, such as the Otter, Badger, Skunk, and many others. Furthermore, the families are conveniently grouped into _sub-orders_, according to characters considered to be of greater importance than those which determine genera or families. We may roughly compare this method of grouping to the way in which the soldiers in an army are arranged. Thus, individual men--corresponding to species--are arranged in _companies_, which we may take to represent genera; several companies are united into a _regiment_, just as a number of genera are united into a family; a greater or less number of regiments go to form a _battalion_, in the same way as the families go to form a sub-order; and, lastly, two or three battalions constitute an _army_, which is the complete assemblage, and corresponds, in our rough illustration, to an _order_. We suppose that nine persons out of ten, if asked to give three common examples of land Carnivores, would, almost without hesitation, name the Cat, the Dog, and the Bear. The most accomplished naturalist would be unable to give a better answer to this question, as those three well-known animals are types of the three primary sections into which the whole sub-order is divided, and which may, in fact, be termed respectively the groups of the Cats, Dogs, and Bears. It must be borne in mind, however, that the words are here used in the broadest and most general sense, for the group of “Cats” includes not only the animals properly so-called, but also the Civets, Ichneumons, Hyænas, whilst amongst “Bears” are grouped Racoons, Otters, Badgers, Weasels, and many others.