68 



PIIOCEEDINGS OF THE NATIONAL MUSEUM. 



\0L. XXVIII. 



The internal anatomy of the Oribatidce is quite well known, having 

 })een investigated by Nicolet and later and more thoroughly by 

 jNIichael. The alimentary canal is composed of a pharynx, cesopha- 

 gus. stomach or ventriculus, intestine, colon, and rectum. The 

 (esophagus has, near its posterior part, an enlargement or ingluvies 

 of varying size, according to the species. The stomach is a large sac 

 in the upper part of the abdomen, provided with two large cwca, one 

 each side, reaching back to near the tip of the abdomen. The small 

 intestine is very short and enlarges to the colon, which is separated 

 from the rectum l)y a constriction. In most, if not all, forms there 

 are two large glands, the preventricular glands, which open into the 



ventriculus near the cfeca. 

 The}" are supposed to secrete 

 some fluid useful in diges- 

 tion. Tiie male organs of 

 generation consist of one 

 central testis, usually large, 

 two vasa deferentia, uniting 

 into a ductus ejaculatorius, 

 which opens through an ex- 

 tensile penis. In the female 

 there is a median ovary 

 (sometimes showing traces 

 of division) opening into 

 two oviducts which unite in 

 a vagina: the latter opens 

 through a protrusible ovi- 

 positor. It is possible that 

 the ovary is connected b}^ 

 two tine tubes to an aperture 

 near the anus, and that this 

 is the • bursa copulatrix. 

 Coition, however, has not 

 been ol)served, so it is not certain that the male does not use the vagina. 

 The trachete when present vary much in shape and size. They open 

 at the acetabula of the legs; one or two trachea' proceed from each 

 acetabulum; sometimes very long, and wind about in the body; 

 sometimes short, and again may be enlarged to form air sacs. In 

 Ilojfhulrrnia there are no trachejv, and in Xothriis they are rudimen- 

 tary, and they are lacking in the larviv and nymphs of all forms. 

 There are various excretory organs; one pair, the supracoxal glands, 

 open near the acetal)ula of the second legs; others, the expulsory 

 ^ esicles open on the sides of the abdomen. The Oribatida? have a 

 delicate sense of touch, which resides apparently in the long hairs or 

 setaj upon the legs, i)articularly a verv long hair on the tibia. They 



Fli;. 129. — KkEM.KTS PIl.OSl'S (HER(iANDE). 



