NEUROPTERA, EPHEMERIDA, AND ODONATA 123 



bottom with two pins, the one passing very obliquely 

 through the head and the other through the hind part of 

 the abdomen. Cut away with scissors the dorsal portion 

 of the body wall and immediately beneath it note a light- 

 colored threadlike tube, which is the heart. Ramifying 

 among the muscles are the trachea appearing as minute 

 slender white tubes, which examined in a drop of water 

 under the microscope show spiral thickenings. If near 

 egg-laying time the female will have much of her ab- 

 domen filled with the two ovaries containing many eggs. 

 Two small tubes, the oviducts, pass from the ovaries to 

 the posterior ventral side of the abdomen, where they 

 unite. 



The digestive canal is a tube extending in an al- 

 most straight course from the mouth to the posterior 

 end of the body. The much enlarged portion in the 

 thorax is the crop which receives the food from the 

 esophagus opening from the mouth. The stomach lies 

 next to the crop and leads into the intestine. Several 

 blind pouches, called ca&ca, project forward from the 

 stomach. 



The nervous system is not easy to observe, but if all the 

 other organs are removed from the body, a white mass of 

 nerve matter, a ganglion, about the size of a pinhead may 

 be found on the floor of the thorax and from it two nerve 

 cords extending forward to the mouth where they pass 

 around the esophagus to a large ganglion, named the brain. 

 Two cords also pass backward from the thoracic ganglion 

 through the abdomen and bear several ganglia. All ganglia 

 are collections of nerve cells, whose processes, the fibers, 

 form the cords. 



