6 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



nul organs. Sometimes there are other nerves that extend to the 

 posterior part of the bod^'. 



The reproductive system is often highly developed, and frequently 

 occupies a considerable part of the body. The male testes are large, 

 lobate, and open into two tubes, the vasa deferent ia, which, uniting, 

 form the ductus ej'acutdtorl'tis, which ma}^ open through a penis. The 

 testes are often united. The ovaries of the female (sometimes united) 

 are situate in the middle part of the body, of varying shape, and 

 open into two tubes — the oviducts — which unite to form the vulva. 

 The latter may ha^e a spermatljeca attached, and may open through 

 an extensible ovipositor. In some families the vulva is not a hursa 

 C(>pulatrh\ but there is a special copulator}^ opening near the anus. 

 In other forms the female organs are very difl'erent, as will l)e 

 mentioned under the families. 



Fig. 4.— Legs of various mites. 



in the Gamasida;'. Tyrogh'phidfe, and Oribatidte there are a pair of 

 glands in each side of the abdomen, each opening b}' a pore in the 

 skin. They contain a yellowish, oily liquid, and are considered excre- 

 tory glands; Michael has called tliem expuhory vesidts. In most 

 mites there are several glands in the head region, some of them 

 evidently of a .salivary nature, but others are often present whose 

 function is unknown. Some of them open into the mouth, or pharynx, 

 and others may open at the base of the mandibles. 



In some mites there is a well-developed dorsal pulsating organ or 

 heart, but in most mites it is not present. In these latter there is an 

 irregular motion of the body-fluids kept up by the action of the 

 nuiscles in other movements. Many mites have an elaborate tracheal 

 system for breathing. These tracheae open in various parts of the 



