202 HIROWO ITO 



The nuclear globules in the included portion have completely- 

 disappeared, probably being absorbed by the phagocytes. There 

 are many granular spheres surrounding the newly formed rectum. 

 From this observation we may safely conclude that the mal- 

 pighian tubes in the wall of the larval rectum are at first com- 

 pletely destroyed, and only secondarily do the phagocytes act 

 in this destruction, as in the cases with the silk glands and the 

 salivary glands. Since Samson ('08) has not studied the histol- 

 ysis of the included portion, it is natural that he came to his 

 conclusion. 



In a pupa four days old, the muscle nuclei of the urinary 

 bladder and the common stem have wholly disappeared through 

 the action of the phagocytes and the imaginal cells have increased 

 greatly in number. The coelomic portion lies embedded among 

 the fat-bodies of the ventral region. The cytoplasm is homo- 

 geneous or granular, and stains deeply with eosin . 



It is thought that the function of the malpighian tubes is 

 arrested in four-day pupa. There are many chromatin granules 

 in the ramified nuclei which stain somewhat faintly with haema- 

 toxylin. The lumen is, moreover, reduced in caliber and takes 

 very irregular shape, varying greatly in different portions. The 

 basement membrane now vanishes as a result of the activity of 

 the phagocytes. The latter becomes enlarged; their contents 

 assume a granular appearance. 



In a pupa five to six days old, the imaginal cells gradually 

 migrate to form the imaginal common stem which opens directly 

 to the alimentary canal, as shown in figure 12, and the urinary 

 bladder is not newly formed. The coelomic portion is in the same 

 position as on the preceding day. The cytoplasm is granular 

 and contains many vacuoles which are basal in position (fig. 

 13). The branches of the nuclei are extended and the chromatin 

 granules become very distinct in outline. The lumen increases 

 in caliber and contains some granules near the wall. These 

 granules are the result of the secretory activity of the cells, and 

 they indicate that the formation of the striated border has already 

 set in. A very thin transparent basement membrane appears, 

 which may be considered to be the secretion from the cells. 



