A CASE OF PROLAPSUS RECTI IN DPAGONFLY. 



65 



question, attention is called to fig. 2, which represents a median sagittal 

 section of it. The distal end of the same section is shown in fig. 3 more 

 highly magnified. The body presents itself as a tube with all the parts of 

 the normal hind intestine in such relative positions as they should take, if 

 this were turned inside out and protruded through the anus. In the 

 lumen are found tubules which can without difficulty be recognized to be 

 parts of Malpighian tubules. The tube wall exhibits internally the 

 muscular layer and externally the mucous epithelium. It would be super- 

 fluous to go into details with regard to the histology of these layers in 

 different parts. Suffice it to say that of the three parts before distinguished 

 on the outside of the pendant body, that which directly adjoins the anus 

 represents the terminal portion of the rectum characterized by having low 

 epithelium known as the anal piece (fig. 2, a) ; the middle part is clearly the 

 rectum proper with thin muscular layer and with epithelium made up of 

 glandular cells (r) ; and the last and the largest part is the ileum charac- 

 terized by having folded epithelium and the musculary layer thickened 

 towards the free end'of the body (/). Imbedded in the thxkened muscular 

 layer just mentioned are seen the conducting ducts of Malpigh'an tubules. 

 Further, at the junction of the middle part with the last, there can be 

 recognized some decomposing gill lamella? attached to the epithelium, which 

 at the place has become re-established a. ter the ecdysis. At the free end 

 the tubular body is open, the wall at the extreme end bearing indications 

 of having been mechanically torn off. 



It then lies beyond reach of doubt that the pendant body is nothing 

 else than the hind intestine of the insect, torn off from the rest of the 

 alimentary canal at the posterior end of the pylorus and completely evagi- 

 nated through the anus. 



So far as I am aware, a similar occurrence seems not to have been 

 recorded before from dragonflies or indeed from any other group of insects. 

 Kvidently we have before us a case of very rare occurrence. It is certainly 

 a difficult matter to determine the cause of the prolapsus, although one 



