608 ROBERT MATHESON 



not only lost their cross striations but their fibrillar part as well 

 (fig. 21). The densely staining portion in figure 21 is the rem- 

 nants of the fibrillae undergoing degeneration. The muscular 

 layer now appears as a granular, cellular mass, separated by the 

 undissolved sarcolemma and remnants of the supporting tissue. 

 The nuclei are not so deeply staining nor so prominent as at the 

 time of pupation. Surrounding the fore-gut are found numerous 

 leucocytes which are undoubtedly taking up some of the broken 

 down tissues, as many are seen to contain deeply staining granules. 

 The above described changes are completed about twenty-four 

 to forty-eight hours after pupation. 



The process of liquefaction of the fibrillae continues till about 

 the time of the shedding of the pupal intima. At this time the 

 muscular layers have the appearance shown in figure 22. Here 

 and there are found nuclei undergoing chromotolysis while some 

 are dividing mitotically. The fibrillar structure is practically 

 lacking, while the nuclei and surrounding cytoplasm appear some- 

 what rejuvenated. Many leucocytes are found surrounding the 

 muscular layers and are absorbing portions of the chromolytic 

 drops as may be seen from their contents (fig. 22, I.). We have 

 now reached the end of the histolytic process. The muscular 

 tissue is not destroyed by phagocytic leucocytes but seems to 

 liquefy in place, the process beginning about the nuclei as centers. 

 Undoubtedly, as previously pointed out, some of the debris is 

 engulfed by the leucocytes. This may be seen from their contents, 

 while several have been found actively surrounding small parti- 

 cles. Also in the larval gizzard region the muscle layer is reduced, 

 and the liquefied muscular tissue is taken up by leucocytes which 

 are most abundant in this region. However, the leucocytes do 

 not seem to play an active part in the destruction of the muscles. 



Histogenesis 



Nearly all the methods of muscle regeneration so far described 

 for the fore-gut may be assigned to the following types or modifi- 

 cations of these types: 



1 . The regeneration of the destroyed muscles from mesodermic 

 cells, myocytes, which are found in the coelom near the inner sur- 



