INTERNAL STRUCTURE OF THE GRASSHOPPER. 259 



b. Below the integument is a layer of small flat muscles, 

 the abdominal muscles. 



c. Cut away the integument of the thorax, and notice 

 the large alary muscles, which entirely till the dorsal por- 

 tion of the mesothorax and metathorax. The muscles of 

 the opposite sides of the body are sharply separated, and 

 a thin chitinous partition runs down from the constriction 

 between the mesothorax and metathorax, and separates the 

 muscles of the wing-covers from those of the wings ; and a 

 similar partition from the constriction between the meta- 

 thorax and first abdominal segment covers the posterior 

 faces of the wing muscles. 



d. The space between the muscles of the abdomen and 

 the viscera is filled with a loose network of a light-colored 

 substance, the corpus adiposum. 



e. Running imvards from the spiracles on the sides of 

 the thoracic and abdominal segments notice the tracheae, 

 rather tough transparent tubes, which divide into smaller 

 branches, which pass to the various organs of the body. 



(i.) Remove a small portion of the corpus adiposum; 

 place it upon a glass slide, in a drop of water, gently cover 

 it, and examining it with a magnifying power of about 

 eighty diameters, notice the transparent branched tracheal 

 tubes which ramify through its substance. Notice the 

 spiral elastic fibre which is coiled around the wall of each 

 tracheal tube, and which, by its elasticity, tends to keep 

 the tube permanently open. 



/. Near the dorsal surfaces of the posterior abdominal 

 segments, surrounded by the corpus adiposum and numer- 

 ous tracheae, is the long, light-colored, reproductive gland 

 (Fig. 139, o), which varies greatly in size and shape 

 according to the age and sex of the specimen. 



g. The digestive organs. These are quite dark in color 



