MALPIGHIAN TUBES OF BOMBYX MOKI L. 201 



The cytoplasm is granular and contains large vacuoles between 

 the nuclei and the basement membrane. The nuclei are ramified 

 as in the larval stage. The striated border disappears, probably 

 at the last ecdysis. The lumen is conspicuously reduced in 

 diameter, due to the contraction of the cells. The basement 

 membrane comes in close contact with the periphery of the 

 epithelium, as in the larval stage. 



The included portion of the tube no longer retains its original 

 shape, owing to the histolysis of the component cells. The 

 fragmentation and dispersion of nuclear elements is more active, 

 and the globules begin to migrate from the peripheral portion. 

 Some globules are already being engulfed by the phagocytes 

 (fig. 9). 



In a pupa two to three days old, the massed nuclei of the 

 urinary bladder and the common stem have entirely disinte- 

 grated into globules. The muscular substance has now com- 

 pletely disappeared, being digested by the phagocytes, and the 

 muscle nuclei alone are still intact. A great many granular 

 spheres are found around the muscle nuclei. 



The coelomic portion now lies in the same position as in the 

 preceding day. The cytoplasm is granular in the posterior 

 portion and vacuolated in the anterior. The vacuoles gradually 

 migrate toward the nucleus so as to come to lie between it and 

 the surface of the cells lining the lumen. The ramified nuclei 

 are central in position and contain many fine chromatin granules. 

 Within the lumen are some granules and globules which are 

 strongly eosinophilous. The basement membrane becomes 

 gradually separated from the cells, as is shown in figure 8, and 

 finally it is completely lifted up as a result of a considerable 

 contraction of the cells. A great number of the phagocytes 

 attack the basement membrane, as is shown in figure 11. This 

 observation agrees well with that of Samson ('08), on the mal- 

 pighian tubes of Heterogenea limacodes. Observing the destruc- 

 tion of the basement membrane, both Cholodkovsky ('87) and 

 Ikeda ('13) came to the conclusion that the malpighian tubes 

 of the larva completely disappear. 



