298 FRANCIS A. HULST. 



are to be the permanent nuclei of the adult muscle fiber. It 

 would appear in some rare instances as though several nuclei of 

 an earlier stage coalesced to form the mature nucleus, but it was 

 not observed in a sufficient number of cases to state that such is 

 the case. 



This process of development of the new muscles from imaginal 

 discs is not only well shown by the sections studied, but seems 

 the logical source of new tissues when one considers the general 

 process recognized in embryology of organic development among 

 insects of complete metamorphism. 



GENERAL CONCLUSIONS. 



1. The degeneration of the muscles begins in the thorax when 

 the larva is two-thirds grown, and is due to chemical alterations. 

 Phagocytosis is not a determining factor, though a lyocytosis may 

 be present. 



2. Phagocytes appear in the muscular detritus after the muscle 

 is far degenerated, attracted by a chemotaxis, and remove a part 

 of the necrotic tissue. 



3. The phagocytes are not blood cells, but probably of meso- 

 dermic origin, formed by a proliferation of cells scattered through 

 the connective tissue. 



4. The completion of muscular destruction is the digestion of 

 the sarcolytes either in the phagocytes (intracellular) or by a fatty 

 degeneration of the fragments which are not ingested by cells, or 

 by a digestion by means of a fluid secreted by cells elsewhere in 

 the body (extracellular). 



5. There is no autophagocytosis of muscles. No myoclasts 

 are present, while, on the other hand, the nuclei undergo a disin- 

 tegration and destruction along with the contractile substance 

 and in a similar way. 



6. The regeneration of new muscles of the adult is from the 

 imaginal discs by a proliferation of the embryonic cells which 

 have persisted undifferentiated during the larval growth. 



