MALPIGHIAN TUBES OF BOMBYX MORI L. 205 



crystals, very probabl}^ a urate salt. The basement membrane 

 is thin, structureless, and transparent. 



SUMMARY 



1. The histolysis of the urinary bladder is accomplished in 

 such a way that the basement membrane and the intima are 

 separated from the epithelial cells, with the destruction of the 

 cytoplasm, and then both the nuclei and the basement membrane 

 are ingested and digested by the phagocytes. The intima is 

 cast off from the lumen at the pupation. The muscular sub- 

 stance and the muscle nuclei are completely destroyed by the 

 phagocytes. 



2. The histolysis of the common stem proceeds in a way similar 

 to that of the urinary bladder. The histogenesis of the imaginal 

 common stem takes place by the gradual extension of the imaginal 

 cells which lie at the distal portion of the larval common stem. 



3. The coelomic portion of the malpighian tube passes directly 

 from the larval into the imaginal stage, though it undergoes 

 the dissolution of the striated border and basement membrane. 

 The imaginal striated border and basement membrane are 

 formed by the secretion of the epithelial cells. 



4. The portion of the malpighian tubes enclosed within the 

 wall of the rectum is completely destroyed, along with the 

 histolysis of the rectum. The nuclei break up into globules 

 which are taken up by the phagocytes. The basement mem- 

 brane is attacked and destroyed by the phagocytes. 



5. The function of the malpighian tubes seems to cease during 

 certain periods of metamorphosis. 



