334) • ME, H. M. BERNAED ON THE 



anything but the juices of the prey from entering the alimentary canal. On the sieves 

 in and around the mouths of Arachnids, cf. the section on the alimentary system. 



The flagellum is also clearly a modified bristle ; its position and form in G. arabs 

 are shown in PI. XXVIT. tig. 11/ 



The only otlier Arachuids which can compare with Galcodes in hairiness are tlie Araneae, especially 

 the Aviculariidse. This is very interesting in view o£ the other features, which appear to be primitive, 

 common to the two. I have found no difference in the principle of suspending the setae and spines of 

 Lycosa. The hard chitinous chambers in which the bases of the larger setse are suspended in the softer 

 abdominal region are very much more powerful than in Galeodes, and the chitin is dark red-brown. A 

 comparison of the setse themselves would lead us too much into details, of great biological interest, but 

 not of sufficient morphological importance to claim attention here. 



Of the remaining Arachnids, none are specially remarkable for hairiness ; on the contrary, the 

 Scorpions, Pedipalpi, and Pseudoscorpious are very free from setse. Many Acari, e. g. Trombidium, 

 however, have very specialized setse, and the same is the case with others, at least in their larval stages 

 {Michael, 56). 



I am inclined to think that the hairy condition was primitive, and that it has been secondarily lost in, 

 certain families in adaptation to special conditions of life. There is hardly any Arachnid which has not 

 retained patches of dense setse in some regions of the body, especially around the mouth. Further, there 

 can, I think, be little doubt that the Scorpions have secondarily lost a hairy covering which has, however, 

 left clear traces of its former presence. If a small Scorpion be cleared in cedar oil or glycerine, its 

 cuticle will be seen to be traversed by enormous numbers of large pores. In section, these pores are 

 found not to open at the exterior ; they are, in fact, canals through the so-called cbitinogenous layers,, 

 which stop short at the bard outer glassy layer (PI. XXX. fig. 1). When we remember that the outer- 

 most layer passes continuously over the bristles, it is obvious that on the gradual degeneration and final 

 disappearance of a bristle we should obtain the structure just mentioned, the last part to disappear being 

 naturally the canal through the cbitinogenous layer. 



Perhaps as good a demonstration as can be given that these pores through the cbitinogenous layers 

 were once setal pores is furnished by the pedipalps of Phrynus. In this animal, the pedipalp, in a 

 marked contrast to that of the Spiders, is almost hairless. But the cuticle is channelled through by 

 countless pores. There are, further, longitudinal rows of tubercular elevations of the cuticle, raising 

 small groups (2, 3, or 4) of these channels, like so many irregular fingers pointing in all directions. All 

 doubt that these pores are really setal pores is dispelled by finding an occasional fine seta rising out of 

 one of them, generally from the slope or just below the summit of a tubercle. These setaj are fine 

 cuticular processes with the characteristic structure. 



The setal pore would, no doubt, itself also disappear in time imless it could be utilized for other 

 purposes. I should like to suggest that these canals containing protoplasmic ijrocesses from the hypo- 

 dermis which runs up as far as to the outer hard layer may now be sensory organs, perhaps for the 

 appreciation of changes of temperature. 



Again, the so-called lyriform organs may be setal pores modified after the degeneration of the original 

 setae (see further on this, p. 355) . 



The claws are somewhat remarkable, owing to the fact that their tips articulate wdth 

 the shafts. A long tendon acts as flexor to this movable tip, I have found no extensor. 



The claws on the first pair of legs, w hick act as a second pair of palps, though small 

 and not jointed, are protiusible and are moved by powerful tendons (PI. XXXII. 

 fig. 10). 



