It is, nevertheless, often difficult to determine between the relationships of affinity and analogy, for groups even in close contiguity may also possess both. Thus, the normal _Ichneumones_ have their analogues in the _Ichneumones adsciti_, if the comparison be restricted to themselves, but these revert into the relationship of affinity when a comparison is instituted between them and the adjacent groups on the one side of the _Tenthredines_, or on the other of the _Aculeata_, with which, when a relationship presents itself, it is merely one of analogy. So, also, within the pentamerous _Coleoptera_ we have a relationship of analogy between the _Staphylinidæ_ and the _Histeridæ_, but it becomes one of affinity when it unites them within this section of the class. Innumerable other instances might be given readily, but these will suffice to convey a notion of the relative meanings of the terms, ‘relation of affinity’ and ‘relation of analogy,’ which is all here aimed at. The problem naturalists have to solve is, “What is the natural system?” We can clearly see that the systems adopted are not Nature’s, that they are essentially imperfect, and that the science, even with all the force of the intelligence that has been applied to it, is far from having attained perfection. It still awaits the master mind that shall cope with its difficulties, determine its intricacies, and, threading the labyrinth, guide his enthusiastic disciples into the adytum of the temple. The subjects here brought under view admit of very considerable development, and of strictly didactic and methodical treatment. It has been my object only to gossip upon them, that I might stimulate curiosity to undertake systematic study, by showing how interesting it may become if earnestly pursued, being so fraught with instruction of large compass.