NO. 10 FI£EDINi; UK(;aNS ok AUA( IINIDA — SNOIM.RASS J I 



(Mth), and are thus but little precjial in pdsition. The leglike second 

 appendages, corresponding with the pedipalps of other arachnids, lie 

 entirely behind the mouth (D. l'df>), and are connected with a large 

 ventral plate (II + IIIS) that would appear to be a combination of 

 the deutosternum and the tritosternum, since it bears both the second 

 and the third pairs of appendages. The pedipalps are said by Kucker 



(1901) to be used in common with the posterior three pairs of legs 

 as locomotor organs, while the long slender first legs are held aloft 

 and waved about in the manner of paljjs. The pedipalp coxae, having 

 no association with the nioutii. are in no way involvi-d in the functi<»n 

 of feeding. 



The snoutlike cone thai bears the mouth 01 the palpigrades (fig. 

 ^ I), Mth) has no duplicate in any other arachnid order. The i>art 

 above the transverse mouth .slit is evidently the labrum (Liu), or 

 labrum and epistome. The suboral j^art {IS) is interpreted by Horner 



(1902) as the prosternuni, that is, the sternum of the cheliceral seg- 

 ment ; there is, in fact, no other structure to which it might be referred, 

 and the close associati<jn of the chelicerae with the base of the cone 

 is entirely in harmony with this view. If. therefore, the mouth of the 

 paljiigrades lies between the labrum and the sternum of the first jjost- 

 oral somite, we see here an embryonic condition retained in no other 

 modern adult arthropod. The complete dissociation of the pedipalps 

 from the mouth. Kiistner (1932I)) says, is known otherwise than in 

 the I'alpigradi only in the Jurassic fossil arachnid Slcniarthron of 

 liaase (1890). Haase. himself, regarded the likeness of Stcrnarthrou 

 to the living Palpigrada as so close that he included it in this order. 



The mouth cone of the I'alpigradi suggests the proboscis of the 

 I'ycnogonida, which projects below the chelicerae and between the 

 pedipalps. but the jK'dipaljJS arise, as in the I'alpigradi. from a .sternal 

 plate behind the base of the proboscis. The pycnogonid prolx)scis, 

 however, has an elaborate innervation from a number of apical 

 ganglia that are connected dorsally with the brain by a single nerve 

 trunk, and ventrally with the suboesophageal ganglion by two nerve 

 trunks (see W iren. 1918, and Hanstrcim, 1928). If the apical ganglia, 

 as Ilanstrom contends, rejiresent the frontal ganglion, this gang- 

 lionic complex of the pycnog(jnids has (|uite a different relation to 

 the stomodaeum within the probo.scis than has the frontal ganglion 

 of the arachnids. Moreover, the innervation of the lower half of the 

 pycnogonid proboscis from the pedipalp centers of the sulxjesoph- 

 ageal ganglion does not conform with the idea that this part of the 

 organ represents the sternum of the cheliceral segment. It seems prob- 

 able, therefore, that the pycnogonid jirolx'^ri- i- > strn.inrc indejxMnl- 



