366 Introduction to Animal Morphology. 



Galeodes there are four, but the hinder send off lateral 

 caeca, and two pair bifurcate, so that six pair enter the 

 limbs and palps. In Pentastomum and Listrophorus 

 there are none. In Mites there are eight, often 

 branched, glandular caeca, in Phalangium as many 

 as thirty, in several rows. Usually these do not ex- 

 tend beyond the first or second joint of the limb ; but 

 in Pycnogonum they stretch to the penultimate joint. 

 Sometimes in Spiders these caoca unite into a ring- 

 like stomach, extending backwards into the intestine, 

 which in Galeodes also has one or more caeca : the 

 rectum is globular in Spiders, or long, as in Scorpions. 

 The liver may be absent (Pycnogonidae, Pentastomidae), 

 or a granular envelope for the intestine (Ixodes, 

 Adenopleura), or short, slightly branched pouches 

 (Trombidium), or eighteen closely branched caeca in 

 two groups, one anterior and one posterior (Galeodes),* 

 or a large yellow-brown lobed organ with 2-3 (Spiders), 

 or 4-5 (Scorpions) ducts on each side. In the last case 

 it fills up a large part of the abdomen. 



Opening into the rectum are, in Scorpions, simple 

 or slightly branched canals passing between the lobes 

 of the liver. In Spiders these canals are much branched, 

 with two terminal ducts. In Phalangium and Acarus 

 they are tortuous, unbranched. These may be uri- 

 nary, homologous to the Malpighian tubes of Insects ; 

 they are absent in the Pseudarachnae. Uric acid is 

 found in two gastric caeca in Gamasus. 



The fatty body is found in the abdomen of Mites 

 and Scorpions, but is replaced by the liver in some 

 Spiders. In Mites (Sarcoptes) it sometimes contains 



* Kiitary regards the hinder of these as renal. 



