176 CLASSIFICATION 



condition of our knowledge goes, a good one. But it is of 

 little value as a practical guide, and as a basis for theoretical 

 speculation it cannot be treated as of importance, because the 

 generalisations it makes use of are premature, owing to the small 

 proportion of the forms that have been examined. And even now 

 the groups adopted are known to be subject to many exceptions. 



Thus it begins by a division of Insecta into winged and 

 wingless ; but the winged division is made to comprehend an 

 enormous number of wingless Insects, whole subdivisions of 

 Orders such as the Mallophaga being placed in the winged series, 

 although all are without wings. This first division is indeed 

 entirely theoretical ; and if a classification on generalisations 

 were adopted, it would be more natural to begin with the old 

 division into Homomorpha and Heteromorpha, and treat the 

 Order Aptera as the first division of the Homomorpha, while the 

 Heteromorpha would commence with theEphemeridae andOdonata, 

 in which, though the individual in the early part of the ontogeny 

 is very different from the perfect Insect, there is no marked 

 division of the later larval and the pupal stages. Brauer's system 

 is also defective inasmuch as it takes no account of the embryo- 

 logical or oogenetic processes, though these are of equal import- 

 ance with the later phases of the Ontogeny. Even as regards the 

 division into Orders, it is far from being free from reproach ; for 

 instance, the separation of the Dermaptera from the Orthoptera, 

 while Ehynchota remains intact, although including a more 

 extensive series of heterogeneous forms ; the division of the 

 Neuroptera into widely separated groups, each of which is treated 

 as equivalent to the great Orders, such as Coleoptera (in which 

 Strepsiptera are included), Hynienoptera, and Diptera, is not 

 reasonable. The association of Mallophaga and Termitidae, while 

 Dermaptera are separated from Orthoptera, is also undeniably 

 arbitrary, and other similar disparities are to be seen on 

 scrutinising the details of the system. 



On comparing the three arrangements we have outlined, it 

 will be seen that the chief discrepancies they present come 

 under two heads : ( 1 ) The treatment of the Xeuroptera, opinions 

 differing as to whether these Insects shall be groiiped as a single 

 Order, or shall be divided into numerous Orders ; and as to what, 

 if this latter course be adopted, the divisions shall be. (2) The 

 treatment of the parasitic groups ilallophaga, Aphaniptera, etc. 



