594 MONTGOMERY— MORPHOLOGY OF THE [April 24, 



(7) Microthelyphonida (Palpigradi) . 

 There are no Malpighian vessels but the adult excretory organs 

 are the coxal glands, and have been described by Rucker (1901) 

 and Borner (1904). There is one pair of these extending forward 

 from the third abdominal segment to their opening between the 

 second and third legs ; the great size of these Borner gives as the 

 explanation for the loss of Malpighian vessels. 



(8) Pcdipalpi (Thelyphonida). 



Malpighian Vessels'. — According to Borner (1904) there is one 

 very ramose pair of these; they develop from the entoblastic ster- 

 coral pocket near its posterior end (Laurie, 1894). 



Coxal Glands. — These are strongly developed, function in 

 postembryonic life, and their ducts open on the third pair of coxse 

 (Borner). 



(9) A ear ilia. 



My account of this group is necessarily very defective because 

 for the most part I have seen only reviews of the literature. 



Malpighian Vessels. — These seem to be absent in many species, 

 but a pair of them has been described for Ixodes (Wagner, 1894), 

 Gamasidse (Michael, 1892, Winkler, 1888), Halarachne (Kraemer, 

 1885), and Tyroglyphid^e (Nalepa, 1884, 1885, Haller, 1880). In 

 the nymphs of^ Gamasids these penetrate deep into each leg. For 

 Bdella Karpelles (1893) ^^^'^ described an unpaired excretory organ 

 of entoblastic origin opening into the rectum. 



Caudal {Proctodceal) Excretory Organs. — These are ijrinary 

 structures opening at the posterior end of the trunk without con- 

 nection with the mid-gut, and are tubular or saccular, closed in- 

 ternally. These may be present (i) when the intestine is provided 

 with an anus, as in Hydrodroma (Schaub, 1888) ; or (2) when the 

 mid-gut ends blind and has no anus, as in Prostigmata (Thor, 

 1904), Gamasidse (Michsel, 1892, 1895), and Troinbidium (Crone- 

 berg, 1879, Henking, 1882). The suggestion was made by Thor 

 that the second type probably represents a rectal bladder with 

 Malpighian vessels that have become separated from the mid-gut. 

 But the first type, that has an opening separate from the anus, can- 



