128 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



1934)- The maxillary glands are usually simple tubes or sacs, but 

 the antennal glands may take on a highly complex structure. 



The coxal glands of Lhnulns are a pair of large brick-red organs 

 lying in the sides of the prosoma. Each organ consists of four suc- 

 cessive glandular lobes arising from a common longitudinal stolon 

 composed of numerous connecting tubules, and of a long coiled duct 

 that proceeds from an end-sac in the fourth lobe and opens behind 

 the base of the fifth appendage (third leg). According to Patten and 

 Hazen (1900) the nephridial lobes are developed from masses of 

 mesodermal cells derived apparently from the somatic walls of the 

 coelomic sacs of the second, third, fourth, and fifth somites. Similar 

 masses of cells in the first and sixth somites degenerate and disappear. 

 The duct arises as a tubular diverticulum of the fifth coelomic sac, 

 which latter becomes the fourth nephridial lobe. A short terminal 

 part of the definitive duct is formed as an ectodermal invagination at 

 the external orifice of the mesodermal duct. 



The coxal glands of Arachnida are best known from the work of 

 Buxton (1913, 1917, see also Petrunkewitch, 1933, and Chickering, 

 1937). A relatively primitive condition is found in the araneid groups 

 Liphistiomorphae and Mygalomorphae, in which each gland has two 

 saccules, one in the third, the other in the fifth segment, both con- 

 nected with a long convoluted tubular labyrinth, from which two 

 outlet ducts proceed to the exterior, one opening behind the third 

 appendage, the other behind the fifth. Such an organ would appear 

 to be a composite structure formed by the union of three consecutive 

 segmental glands. In certain genera of the Amblypygi group of the 

 Pedipalpida the gland of the fifth segment is shown by Buxton (1917) 

 to be an independent organ opening separately on the fifth segment. 

 In the Uropygi each gland has two saccules but only a single opening, 

 which is on the third segment. All other Arachnida have but a single 

 saccule for each lateral gland and a single outlet, but the opening is 

 at the base of the second appendage (pedipalp) in Solpugida and 

 Palpigradida, at the base of the third appendage (first leg) in Ara- 

 neida, excepting the two groups above mentioned, and at the base of 

 the fifth appendage (third leg) in Scorpionida and Phalangida, as 

 in Limulus. Buxton calls attention to the correspondence of the 

 coxal glands of Solpugida and Palpigradida with the salivary glands 

 of Onychophora, the organs in each case having their opening on 

 the second postoral body somite. 



Studies on the development of the arachnid coxal gland appear to 

 leave no doubt that the organs are derivatives of coelomic sacs with 

 coelomoducts formed as direct diverticula from the sacs as are the 



