[Berl. Entomol. Zeitschrift, Band LVIII. Jahrgang 1013.] 211 



On the Rectal Tracheal Gills of a Libellulid-Nymph 

 and Their Fate during the Course of Metamorphosis. 



By K. Oguma, Sapporo (Japan). 



With Plate III, IV and a Textfigiire. 



Contents. Page 



1. Introduction 211 



II. Material and Methods 213 



III. The Rectal Tracheal Qills in the Last Nymphal Stage. 213 



Relation between the Alimentary Caiial and the Tracheal System 



Structure of the Rectal Gills ; 



The Cells of the Epithelial Cushion 



Miiscles and Tracheal Branches in the Rectum 



IV. The Rectal Tracheal Qills of Imago ready to emerge . .217 



Surface Observation 



Exuviae of the Gills 



The remaining Rectal Gills 



V. The Rectal Tracheal Qills of Immature Imago .... 219 



Surface Observation 



Observation in Sections 



VI. The Rectal Traheal Qills in Mature Imago 220 



VII. Histological Study on the Elimination of Rectal Qills and 221 

 the Regeneration of Epithelium and Fat Cells .... 

 Prolongation of the Epithelial Tissues of both Ends of the 



Branchial Parts 



Significance of Falling off of the Epithelial Cushion .... 



VIII. Summary 223 



Bibliography 



Explanation of Plate 



I. Introduction. 



After the publication of Palmen's work i) on the tracheal System 

 in dragonfly-nymphs, Hagen has come to an opinion adverse to that of 

 Palmen concerning the fate of the rectal tracheal gills of the insects in 

 question. Prof. Hagen says: „Dr. Palmen's Angabe, daß das Gewebe der 



^) Palmen: Zur Morphologie des Tracheensystems. 1877. 



V 



