PEEFACE. 



SOME years ag'o Dr. W. F. Purcell of the South African Musoum at Capetown kindly 

 offered to place at the disj^osal of one of lis, wlio had long been engaged in the study 

 of one of the suborders of Opiliones, a certain number of specimens of this order, collected 

 near Capetown, and including a form which he described as " a species with no eyes, but 

 having on either side of cephalothorax above a short tube, resembling strongly an eye-stalk, 

 through which a liquid is ejected, when the animal is irritated." This statement excited our 

 interest in a high degree for the following reason. Whilst the great majority of Opiliones 

 are described as possessing onlj' one pair of eyes, which are sessile, and a few species living 

 in caves in North America are blind, others — and most of them belonging to the suborder 

 Cyphophthalmi — are said to offer very remarkable deviations. Si7'o Latreille (Cyphophthalmus 

 Joseph), Pettahis Thorell and Miopsalis Thorell are said to have severally only one pair of 

 eyes, these being placed on eminences more or less considerable; Stylocellus Westwood is 

 stated to possess in addition to the pair of stalked eyes, a sessile jmir placed in front of 

 the former, and the dubious Gibocellum Stecker is credited with two pairs of stalked eyes, 

 one in front <jf the other. 



For our (jwn j)art we had long entertained strong doubts as to the occurrence of more 

 than one pair of eyes in any Opiliones. As regards C3'phophthalmi in particular — to which 

 suborder the above-named genera belong — our doubts were strengthened by the fact that 

 the openings of the odoriferous glands, which are so characteristic of Opiliones, have not 

 been noticed by the writers in question. Seeing that authors of undoubted ability had 

 mistaken the openings of the odoriferous glands in the common Harvest Spiders, which belong 

 to Phalangioidse, for (sessile) eyes, we were naturally led to suspect that the same mistake 

 had been committed with regard to Cj^ihophthalmi. We should not, however, have ventured 

 to express this suspicion without further justification, because numerous instances that have 

 occurred in the history of science have taught us that such sujjpositions are, as a rule, of 

 little value. Many years ago one of us undertook an examination of the exterior of the 

 only specimen of this suborder which the Museum of Copenhagen at that time possessed, 

 namely, a Siru duricorius Joseph, and as this examination did not lead to any doubt about the 

 correctness of the unanimous statements of previous authors concerning the '■ stalked eyes," 

 a supposition with regard to the eyes in Stylocellus would have been erroneous, as such a 

 guess must have been that the sessile eyes in the last-named genus were the openings of 

 the odoriferous glands. 



The question, however, at once ajjpeared to us in a different light when we received 

 the communication of Dr. Purcell. It struck us immediately that the animal in question 

 must belong to the suborder Cyphophthalmi, and that the "stalked eyes" of this group 

 must be the openings of the odoriferous glands placed on eminences. 



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