586 GEORGE H. BISHOP 



contained in it disappear. Since the spheres which develop 

 from the basophile granules fill the cell, the unavoidable conclu- 

 sion is that both cytoplasm and cytoplasmic fat-vacuoles are ab- 

 sorbed as material for the growth of the spheres (pi. 2, figs. 14, 16). 

 Further evidence is adduced from the cytoplasmic staining 

 reaction of these spheres, and, finally, the peripheral shell, and 

 especially the inside margin of it, is blackened by osmic acid, 

 indicating the presence of fat. 



Stage E late. Figure F shows the later stage of the process 

 which brought about the condition pictured in figure E. A few 

 fat-globules are still present, and a few basophile granules are still 

 in early stages of development. The nucleus has the same aspect 

 as before, except that while earlier stages often show the ends of 

 the nucleus open, in this later stage the nuclear membrane is 

 always intact. The rest of the cell is occupied by the spheres 

 developed from the basophile granules, the interstices of which 

 are filled by a very light-staining cytoplasmic matrix (pi. 2, 

 figs. 14 to 16). 



As the pupa takes on the form of the imago and its tissues 

 demand food material for imaginal development, the trophocytes 

 proceed to the final stages of development and disintegration. 

 The cytoplasmic matrix stains less and less densely, and is re- 

 placed by the growing spheres, until only a clear plasma remains 

 between the latter. The cells become loosened from each other, 

 and round up from a polyhedral to a spherical form, while the 

 interstices so formed fill with lymph from the body fluid. The 

 cells subsequently float free in the body cavity. Finally the cell 

 wall itself dissolves or disintegrates (pi. 2, fig. 14), and the 

 spherical globules are released, to dissolve eventually and lose 

 their integrity in the body fluid. 



The nuclear membrane. The behavior of .the nuclear mem- 

 brane in this process is particularly striking. The nuclear plasma 

 in these fat-body cells appears to become fixed into an exceedingly 

 fine coagulum, so fine that its aggregations cannot be distin- 

 guished under the microscope. It thus gives the appearance 

 of a lightly staining, but entirely homogeneous mass, which 

 tends to take a basic stain as the change in form comes on. The 



