COMPAHATIVE MORPHOLOGY OF THE GALEODID^. 377 



XI. Excretory Organs. 



The Galeodidge have two highly -developed organs of excretion — (1) the coxal glands, 

 and (2) the Malpighian. vessels. 



The Coxal Glands. — These have been often described under various names : " glandes 

 saMvaires," Dufoiu- (31); " glandes stomachales," Blauchard (24) ; their true nature being- 

 recognized by Macleod (53) and Stui-any (70). No full account of them, however, 

 has ever been given. 



Trom the apertui-e, which is found in the folds of the skin between the coxa; of the 

 3rd and 4ith segments, the duct runs backward. After making many coils behind the 

 central nerve-mass, it bends forward again almost as far as to its aperture, appearing, 

 m Bhax, to end at the chitinous plate above described (PL XXVIII. fig. 16,^, eg). 



Laurie has found the coxal gland of Thelyphonus, and I have found that of Phrynus also, opening behind 

 the 3rd limb. According to Sturany, the coxal glaud of the Dipneumones opens in the same place. 

 These, then, form a group distinct from the Scorpions, Tetrapueumoues, Phalangids, and Pseudoscorpious, 

 in which the coxal glands open behind the 5th limb, although the two groups are connected by cases in 

 which traces of coxal glands are found on both the 3rd and 5th limbs (19, 70). The complete absence 

 of all traces of coxal glands on the -ith limb could, if these glands are homologous with tracheaj, be 

 explained by assuming that the original specialization of the invagination on this limb was for respiration, 

 an arrangement which has persisted in Galeodes. 



In all the Galeodes examined, the duct of the gland, on reaching the chitinous plate, 

 develops a great mass of tubules which fill up the spaces between the other tissues. 

 The masses of tubules of the two ducts fuse to form a barrier right across the cephalo- 

 thorax ; through this the blood must filter on its way back through the body towards 

 the abdomen. 



A simjjler condition was, as above described, found in a hungering Rhax. Whether 

 the more complicated condition found in the genus Galeodes is a periodical or a 

 permanent variation, I have been unable to ascertain. It was noticed by Dufour. 



i'he main duct is, as a rule, comparatively free from connective tissue. Where, however, 

 it is thrown into coils, the connective tissue is more pronounced in order to regulate 

 the How of blood between them ; these blood-passages are richly supplied with tracheae 

 (PI. XXXIV. fig. lUj. The cells which comj)ose the waU of the main duct are long ovals, 

 as shown in the same figure. They appear to rest upon a hyaline membrane which dips 

 down between the rounded outer ends of the cells. In this romided outer end the staining 

 strands within the protoplasm are arranged in a characteristic manner. Within the body 

 of the cell they stream inwards like a tangle of hair, showing no regular striation. 

 This streaming ceases after running through about | or | of the length of the cell, and the 

 rest is clear, with, however, a granular wall facing the lumen of the tube. The nucleus lies 

 in this clear space, and is sometimes deeply stained and small (2-3 ^), sometimes large 

 (6 i/j) and vesicular, with deeply-staining granules. 



This description of the main duct agrees fairly well with that of Chernes, although in the latter case 

 certain details were not visible, and the lumen of the tube was relatively much smaller. On the other 

 hand, the long oval cells differ greatly from those composing the main duct in the coxal glands of Scorpio,. 



SECOND SERIES. — ZOOLOGY, VOL. VI. 50 



