604 ROBERT MATHESON 



enlarges and the greater portion migrates towards the distal sur- 

 face (figs. 27 and 28, m.)- Each cell, however, retains a narrow 

 protoplasmic strand connecting it with the basement membrane 

 (fig. 28, st). A cell wall is always present and well defined. The 

 nuclear spindle is nearly always parallel to the long axis of the 

 intestine and is placed at the inner side of a large vacuole. The 

 presence of a vacuole in every dividing cell, together with its 

 staining reaction, clearly prove that these cells belong to the ordi- 

 nary larval epithelium and are not tracheal cells which have mi- 

 grated through the basement membrane, as Anglas ('04) thinks 

 is the origin of the replacement cells in the Hymenoptera. The 

 only method of cellular increase in the fore-gut epithelium is by 

 indirect divisions. Shortly after pupation one finds scattered 

 cells undergoing division in the larval gizzard region. The num- 

 ber gradually increases, reaching its maximum shortly after the 

 shedding of the pupal intima. Then follows a gradual reduction, 

 till division ceases just before the definitive formation of the imag- 

 inal intima. The cellular increase is greatest in the larval gizzard 

 region. 



HISTOLYSIS AND HISTOGENESIS OF THE INTESTINAL MUSCLES 



Histolysis 



Before attempting a discussion of the histolysis of the muscles 

 in Corydalis it may be well to present as briefly as possible the 

 current interpretations of so complex a phenomenon. At present 

 there are several theories, each apparently well founded upon 

 observed facts: 



1. That of the leucocytic phagocytosis of Kowalevsky, Van 

 Rees, and Mercier. According to these workers the muscles are 

 attacked, broken down and engulfed by leucocytes before any 

 chemical changes visible under the microscope have taken place 

 within the muscle substance. Digestion of the debris occurs 

 within the leucocytes. 



2. That of the modified leucocytic phagocytosis of Loos, Batail- 

 lon, and Mercier for Amphibia; Deegener, Vaney, Verson, an.d 

 others for insects. According to this theory there is, first, a 



