A Case of Prolapsus Recti in Dragonfly. 



By 



Kan Oguma, 



College of Agriculture, Sapporo. 



In a collection of dragonflies made by one of our students last year, I 

 found a specimen of SomcitocJdora viridiaenea Uhler which showed a 

 curious white body hanging at the anal end. The collector stated that he 

 caught the specimen near Sapporo while it was flying in a wood. The 

 specimen was brought to me in the living state. At first I took the white 

 body for exuviae of the rectal tracheal gills, which remained attached 

 to the nymphal skin after the last ecdysis. A closer examination, how- 

 ever, has revealed at once that that was not the case. 



The pendant body was 6 mm. long and club-like in shape. It hung 

 down perpendicularly from the anus with the thicker end below. With 

 the naked eye the following three parts, marked off from one another by 

 distinct constrictions, could be distinguished on it : firstly, a short, narrow, 

 and cylindrical stalk-like part in direct attachment to the anus ; secondly, 

 a middle part thicker than the preceding and provided with several 

 longitudinal furrows on the surface; and thirdly, the thickest and largest 

 distal part, fleshy in appearance and showing numerous irregular folds on 

 the surface (fig. i). 



The specimen, together with the peculiar body in question, was fixed in 

 Gilson's mixture. The latter was then cut off at the point of attachment to 

 the anal opening. It was afterwards imbedded in paraffin and laid out into 

 sections for studying. 



The facts gained under the microscope proved that we have here to 



