36 Sensor}/ Hairs 



Thorell states {f, p. 678, Note 2), " Fateor tamen, satis dubium mihi videri, Opilionem oculis 

 sex praeditum (Phalangiiim (Hexomma) vulcanicum Dol.) in rerum natuia existere ! " Amongst 

 Laniatores Octophtludmas marginatus has, according to Wood (pp. 439, 44'0), foui- pairs of eyes, 

 but this animal has never since been mentioned b^f any writer. Finally, two pairs of eyes 

 were ascribed to Phalangodus (Ferefriiis) cjuadnoculatus, by L. Koch (a, p. 880); but Stirensen 

 (e, p. 75) has ascertained by examination of Koch's original specimen that one pair of these 

 " eyes " are merely grains on the ocular protuberance. 



B. The Organs of Sensation of the Skin\ We have found various organs in Opiliones 

 which undoubtedly serve purposes of sensation, and which may be i-eferred to two classes, 

 viz. peculiarly developed hairs and the so-called lyriform organs. 



We have searched with great attention for peculiarly developed hairs in Cyjihophthalmi, 

 and we have found them in three places. On examining the skin of an adult Puvcellia, which 

 had been cleaned by means of caustic potash, we noticed peculiarly developed hairs in two 

 places on the surface of cephalothorax. Exactly on the spot on either .side where the eye 

 is placed in Stylocellus, a little inside the lateral margin of cephalothorax and a little in front 

 of the tubercle in which the odoriferous gland opens, a solitary seta was found, many times 

 longer and thicker than the very fine and short hairs which occur scattered over the surface 

 of cephalothorax. Another peculiarity of this seta is that it is placed on a small hollow knot. 

 In young individuals the same bristle (PI. III., fig. 3 g, s') is found placed in the same manner. 

 In the adult Fettalus hrevicauda Pock.- this bristle is very conspicuous, even when looked for 

 by means of a pocket lens. The area round its point of insertion is considerably raised and 

 shows a different sculpture from that of the surrounding parts ; it is found also in the young 

 of the same species, but the place of its insertion is less marked. We have looked in vain for 

 this bristle in the other blind species of this group ; but we do not feel justified in saying on 

 that account, that it is absent altogether, because we have seen only one specimen of Ogovia, 

 and we have not examined specimens either of Siro or of Parasiro especially prepared for this 

 search. Both in Ogovia and in the other genera it must be supposed to be placed, if it does 

 exist, near or on the cone in which the odoriferous gland opens, but if the bristle is either 

 broken on the specimen examined or not distinguished by special size, it would be difficult to 

 find it without previous preparation for that purpose, or to distinguish it amongst the other 

 scattered bristles. We even consider it very probable that this bristle does occur in the other 

 genera, because Joseph (c, p. 20) says of Siro cyptiopselaphus Jos. — a species which we do not know : 

 " Eyeless, but furnished with two long tactile hairs instead of eyes, which are placed on the lateral 

 conical protuberances ^" We consider it extremely probable that the long hairs which Joseph 

 describes as placed on the lateral conical protuberances, on which the stink glands open, 

 correspond exactly to the bristles which we found in Purcellia and Pettalus between the 

 lateral margin of cephalothorax on either side and the cone with the opening of the gland, 

 which here occupies a more dorsal position. 



We may remind our readers that Grassi and we ourselves have examined a very 

 remarkable hair, evidently sensory, in the blind Koenenia mirabilis placed in the very 



1 The investigation of these organs has been performed the bristle in Purcellia. 

 by H. J. Hansen alone. " According to Joseph {ibid., p. 21) they received their 



^ We did not search for it in P. cimiciformis Cambr. nerves from the suboesophageal ganglion, 

 because we had returned the specimen before we discovered 



