sirrTo structure of secondary systematic value 

 deviate-s fro^i what we consider normal in the 

 froup, then'we must look upon this special de- 

 velopn^nt as a s:oecific character by which the 

 for '.a can be placed inside the prouo to which it 

 naturally belongs; not separated frorr. it. 



It never G:iust be forgotten that actual 

 affinities general ly disclosed in sinilar biolog- 

 ical habits and physiol ogical processes always are 

 manifested by the identical form of those organs 

 which are the essential life organs. 



The externa! -.nanife stations of rel£.tionship 

 are the re före to be souglit in the shaoe of the 

 organs of nutrition, reproduction and loconotion 

 and the association of insects nust te suoported 

 by a honologous developmerit of all the essential 

 organs co^ribined and cannot be based on the shape 

 of a singTe one of those organs howevf r i;riportarit 

 this may appear. Final ly, shall our syste-natic 

 arrangements, which af ter al 1 are bound to be im- 

 perfect .lust to scoe extent succeed in expressing 

 natures's own thoughts, then a v;ell t ra ined mind 

 and a natural sys temat ic instinct is required to 

 decide on v/hich co:Tibination of characters should 

 be considered tyoical and instrumental for the de- 

 teniination of a family with its higher and lower 

 groups. 



ovveden has had a dipterologist v/ith this in- 

 stinct highly de-^eloped, namsly the prominent 

 president of ivongelige Vetenskages Akademien, 

 Professor G, F. FaTlén. 



Tiie descrictions on which he has based and 

 alnost created the Swedish Dipterology evince 

 his profound perception of na tu re ; e\ren the 

 family arrangenients established by him testify 

 about the sarrie natural instinct. He did not 

 ha\re the opportunity to enter into any conpara- 

 tive morphological studies, a requirement still 

 unacco-fiplished in our special branch, and has 

 for that reason not or not always been able to 

 exoress with sufficient clearness and in definite 



