PRESIDENT’S ADDRESS. 339 
respiratory structures— these in some instances resembling in 
some degree the primitive form but not occupying position pre- 
viously pre-empted by wings. 
The bearing of these conclusions on the early phylogeny of 
the group of insects is evident and we are practically forced to 
carry the origin of the group back more remotely in time to connect 
it as seems necessary with a primitive, wingless, tracheate ancestor. 
The elaboration of such a phylogeny in so far as the evidence may 
justify is beyond the scope of this address but its general bearing 
may be indicated in graphic form by adaptation of the diagram 
showing the distribution of different groups of insects in time. 
The diagram adapted from latest edition and translations of Zittel’s 
Paleontology is of course poorly adapted to show the present views 
of direct affinity but will serve our purpose to indicate time of 
appearance of different orders. 
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