FOR instance, the names of plants, of minerals, and of geological strata, may be taken from the places where they occur conspicuously or in a distinct form; as _Parietaria_, _Parnassia_, _Chalcedony_, _Arragonite_, _Silurian_ system, _Purbeck_ limestone. These names may be considered as at first supplying standards of reference; for in order to ascertain whether any rock be _Purbeck_ limestone, we might compare it with the rocks in the Isle of Purbeck. But this reference to a local standard is of authority only till the place of the object in the system, and its distinctive marks, are ascertained. It would not vitiate the above names, if it were found that the _Parnassia_ does not grow on Parnassus; that _Chalcedony_ is not found in Chalcedon; or even that _Arragonite_ no longer occurs in Arragon; for it is now firmly established as a mineral species. Even in geology such a reference is arbitrary, and may be superseded, or at least modified, by a more systematic determination. _Alpine_ limestone is no longer accepted as a satisfactory designation of a rock, now that we know the limestone of the Alps to be of various ages. Again, names of persons, either casually connected with the object, or arbitrarily applied to it, may be employed as designations. This has been done most copiously in botany, as for example, _Nicotiana_, _Dahlia_, _Fuchsia_, _Jungermannia_, _Lonicera_. And Linnæus has laid down rules for restricting this mode of perpetuating the memory of men, in the names of plants. Those generic names, he says[38\4], which have been constructed to preserve the memory of persons who have deserved well of botany, are to be religiously retained. This, he adds, is the sole and supreme reward of the botanist's labours, and must be carefully guarded and {305} scrupulously bestowed, as an encouragement and an honour. Still more arbitrary are the terms borrowed from the names of the gods and goddesses, heroes and heroines of antiquity, to designate new genera in those departments of natural history in which so many have been discovered in recent times as to weary out all attempts at descriptive nomenclature. Cuvier has countenanced this method. 'I have had to frame many new names of genera and sub-genera,' he says[39\4], 'for the sub-genera which I have established were so numerous and various, that the memory is not satisfied with numerical indications. These I have chosen either so as to indicate some character, or among the usual denominations, which I have latinized, or finally, after the example of Linnæus, among the names of mythology, which are in general agreeable to the ear, and which are far from being exhausted.' [Note 38\4: _Phil. Bot._ 241.] [Note 39\4: _Règne An._ p. 16.]