Rnial Traclical Gilb. 219 



It is interesting that the similar occurence is fouiid also in the hind 

 intestine. Whether any secretion M, however, gives rise to the falling 

 Operation or not, is not yet cleariy determined. The renewal of the 

 epithehum is completed in the case of such beetles by the tnulti- 

 piication of crypts, which are found scattered aronnd the mid-intestine 

 and by the spreading of those newly formed cells lipon the naked basement 

 inembrane, while in dragonfies the regeneration is effected in an other 

 way as will be stated later on. 



The intermediate space of the basal cushion is still occupied by a 

 large niass of cells and several leucocytes as well as the muscle fibres of 

 circular layer which have gradual grown. The developmcnt of the 

 longitudinal nuiscle layers between every two double gill rows is very 

 remarkable. 



V. The Rectal Tracheal Gills of Immature Imago. -) 

 Surface Observation. 



Though the abdomen is not yet completely stretched to füll length, 

 it attains a length much greater than that of the nymph, also causing the 

 aliinentary canal to grow much longer. The stoinach still holds the 

 longest portion of the whole canal, being scarcely iiiodified froni the 

 precediiig stage, and remarkable changes have taken place in the parts 

 posterior to the ileum. The ileum, which was slender in the preceeding 

 stage having fine longitudinal foldings on its surface, has become as thick 

 as the stomach in its diameter, develops on the surface much deeper 

 folds, both longitudinal and transverse. This phenomenon is caused by a 

 vigorous multiplication of epithelial cells which has effect to increase the 

 intestinal surface. The anterior part of the rectum where the gills rest, 

 is considerably shortened in length, showing many tranverse parallel 

 folds which indicate the positions of the lamellae (fig. 11 RQ), and six 

 double rows of gills are quite distinctiy observed. owing to constriction 

 of intermediate portions of the rows. The posterior or postbranchial rectum 

 gives rise to several evaginations just behind the branchial part (fig. 10 

 und 11 ev), these being due to an intensive incermcnt of the epithelial cells. 



Of the changes of the tracheal System the most notable is that all 

 of the tracheal branches entering the gills have now become scarcely visible. 

 Observation in Sections. 



Owing to the approach, of both the anterior and posterior ends 

 of the branchial port of rectum, which occured in the previous stage, 



^) I n t h e ni i d - i n t e s t i n e, by a certain fluid secreted out of the crypt- 

 neck-cells the contraction of crypt muscles, is loaded with some pressure 

 and subscquently floes between the chitin lamella of epithelium and the 

 basement membrane, so as to result complete Separation of both the 

 structures i Rengel, p. 446). 



-| An imago that has completely emerged from the nymphal skin, has 

 soft wings in which the pigment is not yet developed, and the abdomen 

 is incompletely stretched. 



