^\2 K. Ognma: 



Tracheenkiemen des Afterdarms nicht aligeworfen wird, sondern in der 

 hnago verbleibt, ist in dieser Allgemeinheit nnrichtig. Bei Bpilheca bi- 

 maciilata aus Europa und bei E. princeps aus Amerika bleibt stets der 

 ganze Apparat in der Exuvienhaut und geht nicht in die Image über. 

 Ich meine mit „stets" natürlich nur die Zahl der mir vorliegenden Häute, 

 bei der ersten Art 24, bei der zweiten über 100. Further: „Durch Auf- 

 weichen habe ich deutlich nachweisen können, daß die ganzen Kiemen 

 nebst der sie innen bedeckenden Membran völlig erhalten in der Exuvie 

 zurückbleiben, und ein im Ausschlüpfen begriffenes Stück zeigt, daß sie 

 aus dem Leibe der Image herausgezogen werden und der Darm darüber 

 getrennt wird". M 



Observing the exuviae of a libellulid-nymph with special attention, 

 one will always find the remnant of a semitransparent body attached to 

 theanus at its one end. Further if the exuviae be that of the last moult, with 

 the aid of a microscope, one will be able to detect without difficulty 

 groups of large cells which one qould readily suppose to be the hypodermic 

 epithelial tissue building up the underlining wall of cuticle of the gills. 

 Thus Hagen's view is appearently verified. Shortly after bis publication 

 concerning this problem he abandoned his former view that the gills in 

 dragonfly-nymphs are never transferred into the adult, but remain in the 

 exuviae, since he had met with an exception in Hiipliaea. observing the 

 nymphal side gills that still exist in the stage of imago -i. But the side 

 gills of this dragonfly are very different in nature from the rectal gills 

 of other libellulids, so that we must exclude the fact of continuance of 

 the side gills from our consideration of the rectal gills in general. More 

 recently, in 1905, Scott ascertained again that the nymphal rectal gills are 

 not present in imago of Platlieiuis lydia. -\ 



Now the question is: whether the rectal tracheal gills are transferred 

 into the adult body or are completely free from the imago, remaining 

 in the exuviae when the last moult ends. If Palmen's view be correct 

 what is the fate of these useless organs for aerial life? Or if we take 

 Hagen's opinion as correct in general, there arises a question; what are 

 the changes undergone during the ecdysis in the alimentary canal of this 

 kind of insect? The following study is undertaken to determine the 

 truth of the matter. 



1) Hagen: Zool. Anz. III, 1880, p. 159. 



-) Hagen: Zool. Anz. III. 1880, p. 304; Korscheit und Heider: Vergl. 

 Embryol. I. 1890, p. 850; Deegener: Handh. Entom. von Schröder 1913, 

 p. 348. 



■') Deegener: loc. cit. 1913, p. 347; tlie original paper of Scott was 

 not accessible to nie. 



