316 MK. H. M. BEEXARD ON THE 



the first segment, by the shifting forward of the pedipalps, when tlie chelicerse left the 

 ventral surface. I therefore cannot follow Croneberg (28) in his endeavour to deduce 

 these parts from fused limbs. Such a derivation brings hopeless confusion into tbe 

 segmentation, where none really exists. The solid chitinous framework round the posterior 

 portion of the beak is necessary to counteract the action of the muscles which expand 

 the CBSophagus for the pumping-in of the food (PI. XXVIII. figs. 3, i, 5). The 

 significance of this position of the pumping-apparatus in the Galeodidse, viz. Avitliin the 

 beak, will be referred to later, in the section on the alimentary canal. 



From the description above given of the origin of the beak of Galeodes, it is clear that it raust be 

 considered to be a primitive Arachnidan characteristic, since it arose as a natural consequence of the 

 shifting of the chelicerse and of the pedipalps to positions above and at the sides of the prostomium. 

 We have abundant evidence among the Arachnida that the beak was, as contended, a primitive structure. 

 In Thelyphonus, where the fusion of the basal joints of the pedipalps has rendered a beak, as such, 

 unnecessary, it nevertheless persists : that is, it is in a position where it could not well have been 

 ■secondarily developed. Examination further shows that here also its floor contains, like that of 

 Galeodes. a chitinous plate somewhat folded anteriorly, which can be traced in sections to the transverse 

 infolding of the cuticle at the anterior end of the large sternite of the 4th segment {cf. p. 312). This 

 infolding is apparently the sternal surface of the 3rd segment, crushed in by the enormous backward 

 growth of the coxse of the pedipalps (PI. XXVTII. figs. 11, 12, 13, 14). This beak, like that of Galeodes, 

 •contains the sucking-apparatus. 



The Pseudoscorpions * and the Gamasidce t are the only other Arachnids known to me which possess 

 well-developed beaks, but the mouth-parts of all the other Arachnids can be best deduced from a 

 primitive beak which has been variously modified. 



Starting from Galeodes (PI. XXVIII. fig. 5), with the mouth at the tip of the beak, we have a 

 complete series which shows the gradual reduction of that organ. In the Chernetid;e (fig. 10) the 

 mouth lies ventrally, in a labrum with a dorsal keel, the pointed labium fitting into the oral aperture; 

 the lining of the mouth is finely striated transversely. The next stage is that of Scorpio (fig. 9), in 

 ■which the dorsally-keeled labrum, though of considerable length above, is shortened ventrally, the 

 mouth having travelled back towards the body, so that it is impossible longer to speak of a beak. The 

 shortened labium is, however, still a pointed median process, as in the Chernetidse. 



In Phrynus (fig. 7) we have a process almost the opposite of that in Scorpio, viz. a great reduction 

 of the labrum, while the long pointed chitinous support of the labium remains as an anterior prolongation 

 of the first clear sternite. This labium has two divergent set;e at its tip, as in Galeodes. In marked 

 contrast to Thelyphunus, where the beak has been enclosed between the pedipalps, in Phrynus the 

 labrum and labium seem to have been forced apart by these same limbs. The mouth, which is 

 immediately under the labrum, is thus no longer bounded ventrally by the labium, but by the pedipalps, 

 which meet in the middle line. The labrum, though greatly reduced, is quite distinct and shows the 

 dorsal keel ; it ran best be seen by removing the dorsal shield and bending back the chelicerse. 



* It is worth recording also that the larval Pseudoscorpions are provided with au enormous sucking-beak ; 

 cf. Metschnikofi' (55). 



t Judging from Winkler's figure (76, Taf. iii. 15), this is a typical beak comparable with that of Galeodes, and 

 contains the sucking-apparatus along the greater part of its length. Winkler, however, calls the labium the maxillae. 

 The long pointed process which he calls the under-lip must be some specialized structure, although its superficial 

 resemblance to the process in Phryiws, which I believe is a true under-lip, is certainly suggestive of an interpretation 

 of the mouth-parts of Phrynus differing from that given in the text. 



