NO. lO IKICDINC ORGANS OF AKAt 1 1 MDA — SNoIm .KASS 17 



posed [n each oilier from opposite sides in such a luaiuier as to enclose 

 a trianjiijulai" space hetween them with tlic mouth at its aj)cx. The 

 coxal spines converge forward toward the oral ajjcrture. The {(mkI of 

 the xipliosurids consists principally of wf)rms and small mollusks. 

 The prey is said hy Lockwood ( iS~o) to he graspe<l !)y the leg pincers 

 and hrought hcncath the hody, where it is lodged hetween the coxae. 

 rile coxae then close against it from the sides and with their spines 

 push it forward to the month, into which it is inserted hy the legs, 

 l.ockwood says the food is rasped and comminuted hy the coxal spines, 

 luit Schlottkc (1935) ohserves that when l.ininliis is fed pieces of 

 tisli, the pieces are gulj)ed down entire, though he admits that shell- 

 tish may be crushed In* the coxae. In any case, the ingested food is 

 ground up in a strong proventricular gizzard before it is passed intr» 

 the stomach. 



Hy contrast with die xipliosurids the Arachni<la are esscntiall\ 

 lic|uid- feeders. The prey is caught by the chelicerae, or the i)cdii)alps 

 if these appendages are chelate, crushed or lacerated, and held in 

 the chelicerae while the exuding body licpiids are sucked out. The 

 arachnids have no chewing organs. The pedipalp coxae, or also the 

 coxae of the first legs, may have lobes functionally associated with 

 the mouth, but they are not masticatory in function, nor do they 

 resemble the coxal lobes of Limuhts. In the Palpigradi there are no 

 such lobes, and the pcdipalps are entirely postoral. If, therefore, the 

 palpigrade mouth structure represents a primitive condition among 

 the .\rachnida, as it appears to do. the arachnid feeding apparatus 

 has been evolved cpiite independently, and has no relation to the 

 feeding organs of modern Xiphosurida. .\11 the arachnids have an 

 efficient sucking jnimp for the ingestion of liquids, but they have no 

 grinding organ such as the gizzard of Limulus. In general, only 

 food in liquid form can pass the arachnid ingestion apixaratus. since 

 usually the entrance is guarded by straining fringes of hairs, and the 

 oesophagus is a very slender tube from the pharynx to the stomach : 

 blood corpuscles and spores, however, may be carried in sit'spcnsion, 

 and in the phalangiids, it is said, even hard fragments of the food are 

 to be found in the stomach. With some of the arachnids, particularly 

 the .\raneida. the availability of the tissues of the prey is increased 

 by the practice of cxtraoral digestion. The arachnids possess salivary 

 glands, and large excretory organs, the so-called "Malpighian vessels," 

 discharging through the anus ; the xiphosurids have no .salivary glands, 

 and no excretory organs connected with the alimentary canal. 



Considering the differences above enumerated l)etween the Arach- 

 nida and the Xiphosurida. it is evident that the two groups represent 



