Although this system of the Orders of Insects has some valuable features it is open to very serious objections, to which we can only briefly allude. The Order Hemiptera with its extensive divisions, Heteroptera, Homoptera, Coccidae, and Anoplura exhibiting great differences in structure and considerable divergence in metamorphosis, is treated as only equivalent to the little group Panorpatae (scorpion-flies); these latter being considered a distinct order, although they are not very different in structure or metamorphosis from the Orders he calls Neuroptera and Trichoptera. The arrangement appears to be specially designed with the view of making the Orders adopted in it fall into the two groups Ametabola and Metabola. The propriety of such a course is more than doubtful since very few of the Ametabola are really without metamorphosis, in the wide sense of that term, while the Metabola include Insects with various kinds of metamorphosis. Indeed if we substitute for the term Ametabola the more correct expression, "Insects with little metamorphosis," and for Metabola the definition, "Insects with more metamorphosis but of various kinds," we then recognise that the arrangement {175}is, like all others, a quite artificial one, while it is of little value, owing to the development of so few Insects being hitherto fully ascertained. BRAUER'S CLASSIFICATION. Professor Brauer has recently proposed[110] to adopt 17 Orders or chief groups of Insects, arranging them as follows:— I. APTERYGOGENEA (with one order). 1. _Synaptera_ (= _Aptera_ of our system). II. PTERYGOGENEA (= all the other Insects of our arrangement). 2. _Dermaptera_ (= _Orthoptera_, Fam. _Forficulidae_ in our arrangement). 3. _Ephemeridae_ (= a division of _Neuroptera_ in our arrangement). 4. _Odonata_ (= a division of _Neuroptera_ in our arrangement). 5. _Plecoptera_ (= _Neuroptera_, Fam. _Perlidae_ in our arrangement). 6. _Orthoptera_ (= our _Orthoptera_ - _Forficulidae_ and + _Embiidae_). 7. _Corrodentia_ (= the families _Termitidae_, _Psocidae_, and _Mallophaga_, of our _Neuroptera_). 8. _Thysanoptera_ (as with us). 9. _Rhynchota_ (= _Hemiptera_ with us). 10. _Neuroptera_ (= the families _Hemerobiidæ_ and _Sialidæ_ of our _Neuroptera_). 11. _Panorpatae_ (= the family _Panorpidae_ of our _Neuroptera_). 12. _Trichoptera_ (= the division _Trichoptera_ of _Neuroptera_). 13. _Lepidoptera_ (= as with us). 14. _Diptera_ (= our _Diptera_ - _Aphaniptera_). 15. _Siphonaptera_ (= _Aphaniptera_, a division of _Diptera_ with us). 16. _Coleoptera_ (= _Coleoptera_). 17. _Hymenoptera_ (as with us).