454 MISS A. M. EVANS ON THE STRUCTURE AND OCCURRENCE 



(4) In the Endopterygota fusion of the distal portion of the mouth-floor 

 with the labium. This occurs in the more specialised Coleoptera. 

 Lateral fusion has taken place in the Neuroptcrous forms 

 examined. The Tenthredinere, Trichoptera, and Lepidoptera 

 represent, consecutive stages in the formation of a spinneret, 

 by prolongation of the intimately fused labium and hypopharynx 

 around the opening of the labial duct. 



Finally, I wish to lay emphasis on the tentative character of the " con- 

 clusions " here reached. In certain of the orders and families considered 

 maxillulas were not hitherto known to be present. It is hoped that sub- 

 sequent investigation into the embryological development and morphology 

 of allied forms will reveal the truth with regard to this interesting question. 



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