706 THE PANORPOID COMPLEX, ill-, 



ing method has been adopted : — In ease of characters repre- 

 sented by A or B only, A scores 1, B nil; for tiiose represented 

 by A, B, C, A scores 1, B \, C nil; for those represented by 

 A, B, C, D, A scores 1, B - C - , and D nil ; and so on . Tims 



due allowance is made for the possession of any degree of ar- 

 chaism; and the only condition that scores nothing at all is the 

 most highly specialised condition in each case. In the case of 

 the cross-vein system, there are no less than six evolutionary 

 stages recognisable, which have been arranged in ascending 

 order as A, B, C, D, E and F, with scores 1, \,^., -=j -=jand nil 



o o o o 



respectively ( Section vii . ) . 



In the case of fossil Orders, when the part of the wing show- 

 ing a particular character lias not been preserved, that charac- 

 ter is shown in brackets in (he condition in which it most pro- 

 bably existed in the fossil. It stands to reason that the missing 

 characters, in the Permian and Triassic fossils, will almost cer- 

 tainly, when discovered, prove to have been present in the most 

 archaic condition, A. The only exception made has been in 

 the condition of the wing-coupling apparatus, which cannot be 

 judged, and has therefore been entirely omitted. 



The results obtained from the Table show that the two fossil 

 Orders Paramecoptera and Protomecoptera are the most archaic, 

 the Archetype of the latter scoring 90.0 per cent., and that 

 of the former 86.1 per cent. Next to these comes the Arche- 

 type of the Mecoptera, with 77.8 per cent. The two Neurop- 

 teroid Orders, Megaloptera and Planipennia, have also very ar- 

 chaic Archetypes, with 73.9 and 65.6 per cent, respectively. 

 The Paratrichoptera are the most specialised of the purely fossil 

 Orders, with 66.5 per cent. The two Orders Trichoptera and 

 Lepidoptera, as might be expected, come very close together, 

 with 48.5 and 44.6 per cent, respectively. Finally, as was 

 also very evident from the beginning, the most highly specialised 

 Archetype is that of the Diptera, which possesses only 35.3 

 per cent of the total possible archaic characters. 



The Phylogeny of the Orders of the Complex. 



In Text-fig. 1.12, I have attempted to represent, by means of 

 a Phylogenetic Diagram, the true -relationships of the Orders 

 comprised in the Complex, and their most probable lines of 

 descent. All the known fossils have been made use of; and a 

 series of small numerals are used as indicators for the positions 



