523 



Fig. 122. Regenerated pharyngeal dilator muscle — fresh 

 pupa (1200). 



Pig. 123. The same; fibrils present; striations are already 

 plainly visible below, still developing above. 



Fig. 124. The same — four and a half day pupa. This muscle 

 shows several "roots," which is unusual. The structure of the 

 pharynx is also shown. Note the thick muscle layer (xl200). 



Fig. 125. A branched contractile cell from the crop — four 

 and a half day pupa (xl200). 



Fig. 126. Longitudinal section through the insertions of 

 adjacent body muscles (x800) — adult larva. 



Fig. 127. Longitudinal section of insertion of a larval muscle 

 on the integument (slightly diagrammatic). The spindle-shaped 

 sarcomeres are clearlv seen. Also Krause's ''membrane" (k.m.) 

 (xloOO). 



Fig. 128. Developing "wing" muscles. Transverse section 

 through proliferating myoblasts in prothorax, prior to stage 

 shown in fig. 130. The column of myoblasts on left of figure is 

 growing independently of the lai"val muscles. The others, which 

 are more scattered, are enveloping and drawing together the three 

 degenerate larval muscles — eight hours after defaecation (x800). 



Fig. 129. The same, slightly more anteriorly, showing myo- 

 blasts penetrating into the larval muscle, which is shown in trans- 

 verse section. A leucocyte is also absorbing part of the muscle 

 (X120O). 



Fig. 130. One of the two bands of myoblasts in transverse 

 section ; all larval elements have disappeared — eighteen hours 

 after defaecation (x800). 



Fig. 131. The same, four hours later ; the fine syncytial 

 columns are beginning to form (xlOOO). 



Fig. 132. Diagrammatic section through the thorax, to show 

 the relative size and positions of the two muscle bands (x40) — 

 fresh pupa. 



Fig. 133. The same, four and a* half days later. Note dis- 

 appearance of fat-body, decrease in diameter of oesophagus, and 

 increase in size of muscles (x40). 



Fig. 134. A muscle band in transverse section. More cells 

 have become merged into the syncytium — four-hour pupa (x500). 



Plate XXVI. 



Fig. 135. Longitudinal vertical section through the anterior 

 end of the developing ''wing" muscles — fresh pupa (xoOO). Note 

 three of the syncytial columns (s) applied to the integument, 

 whose cells are now dividing to form the insertion cells. 



Fig. 136. The same, eight hours later (xoOO). Note the 

 long insertion threads, consisting of two cells generally. At x an 

 integumental cell is elongating. 



Fig. 1-37. The same, sixteen-hour pupa. ' The threads have 

 now split and are unicellular, and shortening has commenced 

 (x450). 



Fig. 137a. The same, thirty-six hour pupa. The insertion 

 cells have completely retracted (xoOO). 



Fig. 138, The same, four and a half day pupa (mature). 

 The insertion cells have now broken up into fibrils, on each of 

 which a sarcostyle is inserted (xl20O). 



Fig. 139. This shows five myoblasts each giving off the fibrils 

 which, growing into the syncytial mass, become the sarcostvles. 



