EBERHARTS OUTLINES OF 



fibres, which are not gathered into bundles united by com- 

 mon tendons, or covered by aponeuroses (tendinous sheaths), 

 to form distinct muscles, as in the Vertebrata, but remain 

 separate from each other and only in some instances are 

 united at one extremity by tendons."* 



The Nervous System. This consists primarily of two 

 longitudinal cords, with a knot of ganglion (nerve-centre) 

 for each segment. The position of this is ventral. 



The Organs of Nutrition. These are made up of an 

 alimentary canal with its appendages, and are found in vari- 

 ous stages of development in different insects, the simplest 

 form being a straight tube. 



Circulation. The heart of the insect is a dorsal pul- 

 sating tube, terminating in a large artery in the head. The 

 blood of the insect is seldom red, — generally it is color- 

 less, — bxit sometimes of a yellow tinge. 



Respiration. The insect breathes through little tubes 

 or pores called tracheae, the terminal openings being called 

 spiracles, of which a row runs along each side of the body, 

 there being normally eleven on each side. 



Aquatic insects respire " water mechanically mixed with 

 air," by means of gill -like flattened expansions of the body- 

 wall, called branchiae. Their inner tubes are generally 

 termed bronchial tracheae. 



The Secretive Organs. Says Packard: "The urinary 

 vessels, or what is equivalent to the kidneys of the higher 

 animals, consist in insects of several long tubes, which 

 empty by one or two secretory ducts into the posterior or 



Note. The muscular power of insects is almost incredible. A flea will 

 jump 200 times its own height. Newport mentions an instance where Geotbupbs 

 Stebcobabtpb sustained and escaped from under a pressure of 20 or 30 ounces, 

 the insect itself only weighing about that many grains. 



