THE GRASSHOPPER. 53 



carefully remove the roof of skin included between the 

 two cuts. Observe the thin, longitudinal muscle fibers 

 lining the roof of the abdomen, and the heavy wing mus- 

 cles completely filling the upper part of the thorax. 



I. Tracheae and Ovaries. Press the body walls lightly 

 outward, and observe the numerous white air tubes 

 (tracheae). Observe that the tracheae arise from the spira- 

 cles; that their larger branches unite to form longitudinal 

 passageways along the sides of the body; and that the 

 smaller branches ramify throughout the entire body, con- 

 veying air to all parts. Observe a loose, whitish mass of 

 these smaller branches now lying exposed in the abdomen, 

 on top of other organs. Place a small portion of this mass 

 in a drop of water on a slide. Cover it lightly with a 

 cover slip, and examine with low power to make out : 



1. The branching tracheal tubes. 



2. The spiral elastic fiber which is coiled around the 

 wall of each to keep it open. 



Two large and conspicuous yellow egg masses are usually 

 present in the abdomen of the female. These contain 

 many cylindrical eggs, piled like cord wood in ricks or 

 in tierlike masses. Separate the two masses by pushing 

 a dull instrument between them on the median line. Ob- 

 serve that each egg mass (ovary) has a white tube (an 

 oviduct) leading down to the ovipositor. Carefully re- 

 move the egg masses, and pin back securely both free 

 edges of the skin. 



II. Organs of Digestion. Study the digestive system. 

 The alimentary canal, dark-colored and conspicuous, will be 

 easily seen extending through the body lengthwise. Be- 

 ginning at the mouth, make out the parts of it, together 

 with the accessory organs, as follows : 



1. The mouth opens into an esophagus which extends 

 upward into the head, then backward into the thorax, 

 bending at right angles. 



