522 



Fig. 99. Portion of body musculature of larva in first instar; 

 viewed in tlie living larva througli the transparent integument. 



Fig. 100. A single longitudinal muscle (mucle fibre) from the 

 same, composed of four distinct cells. The insertion of the muscle 

 on an integumentary cell is also seen (xlOOO). 



Fig. 101. Piece of a muscle from adult larva, showing double 

 spiral striations (x900). 



Fig. 102. Muscle nuclei : (a) from adult larva ; (b) from 

 larva in first instar. Note only a slight increase in nuclear size. 

 The older nucleus shows three small nucleoli ; there has apparently 

 been no increase in the quantity of chromatin (xl500). 



Fig. 103. A tracheole from developing forowing of larva 

 eight hours after defaecation. 



Plat® XXIV. 



Fig. 104, Part of degenerating oblique abdominal muscle 

 (fibre) showing a disorganization of the sarcomeres — defaecating 

 larva (xl2D0). 



Fig. 105. A degenerated ventral longitudinal abdominal 

 muscle (fibre) being attacked by leucocytes. Note the degenerate 

 nuclei, fresb pupa (xl200). 



Fig. 106. Dorsal longitudinal muscle, into which myoblasts 

 have penetr^ated, fresh pupa (xlOOO). 



Fig. 107. The same (xl20O). Amoeboid myoblasts hiave 

 entered the extruded sarcoplasm. 



Figs. 108, 109. The same (xlOOO) in various degrees of meta- 

 morphosis. 



Fig. 110. Degenerating circular (oblique) muscle from pro- 

 podeum. Myoblasts are extending over the degenerate fragments 

 of larval muscle. A few leucocytes and extruded degeneration 

 globules are also seen (xl200). 



Fig. 111. A regenerated abdominal muscle, thirty-six hour 

 pupa. Cell limits are still indistinctly visible. Fibrillation has 

 not yet commenced (xl20O). 



Fig. 112. Longitudinal section through proliferating myo- 

 blasts of mesothorax, to form the great ''wing" muscles (x900) 

 — 'defaecating larva. 



Fig. 113. The same, in prothorax; myoblasts extending over 

 a larval muscle, in which striations are still visible — defaecating 

 larva (xl200). 



Fig. 114. The great column of myoblasts in head, being 

 drawn apart into its constituent muscles ( x 800) — ^thirty-six hour 

 pupa. The column, at a much earlier stage, is shown in fig. 91. 



Fig. 115. A small portion of the same, to show traces of 

 the separate myoblasts (xl500). 



Fig. 116. The same, fuUv developed — four and half day 

 pupa (xl200). 



Plate XXV. 



Fig. 117. Longitudinal section througli the head of defaecating 

 larva near mid-line (x600). The oesophagus, salivary duct, 

 pharyngeal dilator muscles and integument are undergoing 

 metamorphosis. 



Figs. 118, 119. A pharyngeal diliator muscle degenerating 

 without the intervention of leucocytes — ^defaecating larva (xl200). 



Figs. 120, 121. Myoblasts overwhelming pharyngeal dilator 

 muscles. In fig. 120 the striations are still present. 



