491 



always of apparently normal structure. But at other times 

 he was clearly dealing with degenerating cells — cells with 

 globulat-ed and highly vacuolated protoplasm, though the 

 occurrence of large vacuoles in the living salivary glands led 

 him to doubt this interpretation. It should be point-ed out, 

 however, that even if a cell stiU has its normal structure, that 

 is nio proof that it is not dead. It may take many hours for 

 the structural symptoms of death to become visible. It is, 

 perhaps, just necessary to add that in whatever condition 

 the tissues may have been when they were fixed, there is no 

 doubt that when they were examined they were dead. It is 

 also worth drawing attention to the fact that Lowne has 

 expressly stated that the larval muscles become functionless 

 some time before phagocytosis commences. The muscles of 

 Galli'phora appear to be very resistant to autolysis; torn -off 

 fragments engulfed by phagocytes still retain their normal 

 structure, yet these are, it is to be presumed, quite "dead." 



When, however, we examine the cells of the adult 

 larva of N a soma no doubts can be left in our minds 

 that death, accompanied this time by active disin- 

 tegration, has occurred, and the most varied types of 

 disintegration are to be seen. All the cells show as 

 a ^mmoji- feature a great hypertrophy. Tliey have often 

 grown to many times the size of the cells of the newly 

 hatched larva; even the nerve cells have grown greatly, though 

 here the increase in size cannot be estimated, as the volume 

 of the nerve fibres is indeterminable. Most of the degener- 

 ating cells present, also, a great nucleolus within the nucleus. 

 Sometimes this may be relatively gigantic and may lodge 

 excretory ( ?) crystals. This in itself lends support to the view 

 that the nucleolus is a structure within the nucleus concerned 

 with excretion — perhaps itself an excretory product, perhaps 

 an excretory "organ." 



The disintegration of the various cells occurs, as we have 

 seen, in many ways. Sometimes before this has had time to 

 proceed very far, phagocytes or embryonic imaginal cells may 

 overwhelm them (many muscles). At other times the adjacent 

 imaginal cells absorb the degeneration products of the dead 

 larval cells directly, either by secreting an enzyme which dis- 

 solves them, or by waiting for them to disintegrate spon- 

 taneously (microscopic examination cannot decide between 

 these two). This is seen in the nerve cells. 



But at other times the larval organs undergo most marked 

 visible disintegrations. The cytoplasm becomes disorganized 

 and may break up into globules or granules, or into a very fine 

 debris, and be cast, as one large globule, or numerous minute 

 particles from the cell, the wall of which itself later dissolves 



