200 HIROWO ITO 



The distal end of the tubes has become narrow and shortly 

 prior to pupation is detached from the rectum. The cytoplasm 

 is homogeneous or very finely granular, and vacuoles no longer 

 occur. The irregularly ramified nuclei are slightly shrunken 

 and contain fine chromatin granules. The striated border is 

 very faint and feebly developed, as is characteristic of the 

 included portion. The lumen of the posterior portion is filled 

 with homogeneous substance, while the anterior portion contains 

 coarse granules. The basement membrane has the same char- 

 acter as in the preceding region. 



The most remarkable histological change takes place in the 

 included portion of the malpighian tubes, in connection with the 

 histolysis of the rectum. The cytoplasm is granular and con- 

 tains some small vacuoles. The ramified nuclei are fragmented 

 into pieces, which form masses containing deeply staining chro- 

 matin in the form of a solid ball (fig. 7). Some massed nuclei 

 have already been divided into globules. The lumen has com- 

 pletely disappeared as a result of the contraction of the epithelial 

 cells. The phagocytes attack the basement membrane which 

 sometimes is found already destroyed here and there, as is shown 

 in figure 7. Such disintegration of the included portion of the 

 malpighian tubes has not been observed by any previous authors. 



3. Malpighian tubes in pupae 



In a pupa not older than twenty hours the cytoplasm of the 

 urinary bladder and the common stem has completely disap- 

 peared. The massed nuclei are now fragmented into globules, 

 which are gradually scattered in the body cavity, as is shown in 

 figure 10. The intima is cast off from the lumen with the last 

 ecdysis. There is no trace of the basement membrane, it being 

 digested by the phagocytes. The muscles are also disorganizing 

 by the attack of the phagocytes. The imaginal cells at the 

 distal portion of the common stem increase in number by multi- 

 plication and gradually take the place occupied by the destroyed 

 epithelial cells. 



The coelomic portion of the tubes is detached from the ali- 

 mentary canal and lies in convolutions among the fat-bodies. 



