COMPAEATIVE MORPHOLOGY OF THE GALEODID.E. 325 



The only other Araclinids with fixed coxal joints to the pedipalps are, I tliink, Theh/phomts and 

 Schizonotus, and (?) some Pseudoscorpious. In Thelyphonus the beak is enclosed between the enormous 

 coxal joints of the pedipalps, ■which thus form on their upper and inner sides a sort of channel in which 

 the beak lies. In Phrymis, we have the coxal joints movable, but the beak as such has aborted in such 

 a way (PI. XXVIII. fig. 7) that the inner opposite faces of the coxie can meet in the middle line. 

 In the Spiders, the coxal joints function on each side of the mouth as accessory mouth-parts*. 

 In the Chernetidse, it is difficult to say for certain whether the coxal joints of the pedipalps are movable, 

 but their lamellate sensory processes (above described) are certainly, in some cases, movable, and serve 

 to hold and crush prey in front of the beak. In Scorpio, the coxfe are movable, but do not appear 

 to be able to close together, owing to the retention of the large labrum between them. These various 

 arrangements will be referred to again in the section on the alimentary system, inasmuch as they are 

 different adaptations to the special manner of feeding of the Arachnids. 



The Belat'tve Developments of Chelicerce and Pedipaljis. — In the Galeodidse, the cheli- 

 cerae have certainly been secondarily developed into their present enormous proportions. 

 In the primitive form, there is no reason to believe that there was any great difference 

 between the development of the cbelicerae and that of the pedipalps, except, perhaps, in 

 length ; sections through their basal regions would probably have agreed in size. We can 

 best explain the conditions in Galeodes by assuming that the chelicerse have greatly 

 developed, while the pedipalps have retained more nearly their relative importance with 

 regard to the remaining limbs. 



In the Araneffi and the Phalangidfe, the same relations subsist as in Galeodes ; the chelicerfe are 

 the principal seizing organs, and are correspondingly developed. In those forms, however, iu which the 

 pedipalps have become the seizing organs, they have, from their greater initial length, more or less 

 monopolized this function, and have been correspondinglj^ specialized. We have thus a series in which 

 the pedipalps progressively increase, while the chelicene recede in importance, having henceforth to fulfil 

 only the quite subordinate function of squeezing juices out of prey already killed or maimed by the 

 pedipalps. In Schizonotns the pedipalps are in the upright, clawing position, and in this animal and in 

 the related Thehjphomis the distal joints have formed a simple kind of nipper. In Phrynns no such 

 pincer is formed at all ; the pedipalps are clawing limbs. In these three we find the pedipalps highly 

 developed, while the cheliccrae are probably in process of reduction, and tending to flatten out in the 

 median plane (PI. XXV^III. fig. 9). Lastly, in Scorpio, the pedipalps are enormously developed, the 

 original clawing action having developed powerful pincers t, while the chelicerse have greatly diminished 

 in size (PI. XXVILfig. 9 6). 



The series of figures 9 a, 9 b, 9 c (PI. XXVII. ), and 9 (PL XXVIII.) represent cross-sections of Galeodes, 

 Scorpio, Obisium, and Thelyphonus (drawn with camera lucida). The great diminution of the chelicerae 

 in Scorpio and Thelyphonus is seen to be a secondary specialization. Both Galeodes and Scorpio 

 depart in opposite directions from the Obisimn type, in which the bases of the limbs are shown of nearly 

 equal importance in cross-section, such being in all probability the primitive condition. 



The great modifications of the anterior segments brought about by the original translocation of the 

 chelicerae are still further complicated by the development and specialization of the pedipalps as a 2nd 



* These are not biting jaws, working within or at the sides of the oral aperture ; such jaws (except, according 

 to my friend Mr. Michael, in some Acari) are unknown among the Arachnids. 



t If the pedipalps of a Scorpion are turned upwards into the sagittal plane, the distal joint will, in closing, be 

 found to move in a clawing direction, /. t'. towards the body. 



