66 Mr. A. Tulk on Obisium orthodactylum. 



the basal joint of the cheHeerse_, and near to the commencement 

 of the claws, a tuft of long pinnate hairs, eight to nine in num- 

 ber, which converge together at their extremities to form a com- 

 plete brush reaching almost to the middle of the claws. 



I had often speculated upon the probable use of this peculiar 

 contrivance, until upon more than one occasion, having placed the 

 animal alive in a glass cell for examination beneath the micro- 

 scope, I observed it very busily engaged in cleaning its long 

 palpi, especially their didactyle forceps, by drawing them repeat- 

 edly between the claws of the chelicerse, the latter being freely 

 rotated during the operation, so as to bring every part of these 

 organs in contact with the combs and hairy tuft. The tarsi were 

 cleaned also at the same time, by applying them against some 

 scattered bristles which project inwards from the coxal joints. 

 Before I had noticed the above facts, my attention had indeed 

 been directed to these comb-shaped organs in Obisium by the 

 very striking resemblance which they bore to the abdominal joec- 

 tines of the scorpion ; and now that we had conclusive evidence 

 of their functions in the one, it became a question whether those 

 of the latter might not perform some similar office. The uses 

 which have been assigned hitherto to these parts in the scorpion 

 by different writers, appear to me far from satisfactory. While 

 their lamellated structure alone has induced some to regard them 

 as external branchise, their situation near to the generative open- 

 ing in both sexes has led others to view them as claspers during 

 the act of copulation, by their plates mutually interlacing with 

 each other ; they have been regarded even as aiding in locomo- 

 tion. It may be objected to the view which I am here disposed 

 to take of their acting as cleansers to the palpi, tarsi and elon- 

 gated portion of the abdomen, that their position is widely dif- 

 ferent in the true as contrasted with the Pseudo-scorpion ; but 

 need we be more surprised at this than that the poison-sac, which 

 in one group of Arachnida is placed within the chelicerse, should 

 in another be transferred to the opposite extremity of the body ? 

 Admitting then that such has been the case in the present in- 

 stance, it may be understood why the combs of the scorpion and 

 each of their separate teeth should be moveably articulated to 

 compensate for the immobility of that part of the abdomen to 

 which they are attached, while such a provision would, for ob- 

 vious reasons, be unnecessary in the little Obisium. 



There is a remarkable agreement, however, in many other points 

 of external structure between these two animals which must not be 

 overlooked, as they tend to support still further the above analogy. 

 Treviranus has noticed the striking resemblance between the palpi 

 and maxillse of an allied genus Chelifer and those of the scorpion, 

 and the comparisan may be drawn more closely still between the 



