58 Mnsdes of the sheath of Ovipositor 



In Nemastoma the muscular stratum of the sheath of ovipositor is attached anteriorly 

 to the outer chitinous sheath near the anterior extremity of the latter; in Phalangioidse, 

 for instance in Acantholojjlius (PI. VI., fig. 1), the middle portion of this muscular stratum (ms) 

 both on the upper and on the under side is fixed anteriorly to the sheath itself, whilst 

 the lateral portions anteriorly bend outwards and a little backwards in order to insert 

 themselves on the skin. Both in Nemastoma and in Acaniliolophus two pairs of muscles 

 are found in front of this muscular stratum, of which the posterior one, which is represented 

 in the whole of its length on PL VI., fig. 1, md, rises from the skin in front of the lateral 

 portions just mentioned of the longitudinal muscular stratum of the sheath, and attaches 

 itself to the sheath, the fibres spreading fan-like ; most of them, and those the strongest, 

 pass slantingly forwards but a few are even directed a little backwards. The other pair of 

 muscles marked me on the same figure, pass on the contrary exclusively obliquely forwards 

 and attach themselves as shown in the figure to a small tendon-like expansion of the sheath 

 a short distance behind the genital orifice. — In Cyphophthalmi there is on the outside of 

 the sheath a thin layer of longitudinal mu.scles of which the fibres run parallel through 

 about the posterior half of the sheath, but afterwards diverge somewhat on the upper as 

 well as on the under surface (PI. IV., fig. 1 t, ms), and finally attach themselves to the 

 sides of the sheath. Anteriorly there is a pair of muscles {md) jjassing obliquely forwards 

 from the skin to the sheath. — As in all Opiliones there is a further pair of muscles, mr, 

 which anteriorly are attached to the posterior extremity of ovipositor, but posteriorly are 

 inserted on the skin. 



We have examined a larger number of these animals than our predecessors and found 

 the arrangement of these muscles somewhat different from what had been stated by them, 

 whereby we have been led to a somewhat different view of them from that entertained by 

 earlier writers. We agree with them all in looking upon the pair of muscles which we 

 have marked inr as m. retractores ovipositoris, and we agree with Sorensen in thinking 

 that the pair of muscles marked mo in Laniatores serve to close operculum genitale ; but 

 we are also of opinion that the pair of muscles which we have marked me perform the 

 same function in Palpatores, although they do not attach themselves to operculum genitale 

 itself but to the sheath at a point closely behind the genital orifice. It is certain, in any 

 case, that their contraction alter ovipositor has been drawn in must have the effect indicated, 

 but it is very possible that this pair of muscles may also serve to expand the sheaths 

 of ovipositor and thus to assi.st in drawing them back when ovipositor is wholly exserted 

 and the sheaths are entirely tui-ned inside out. It may be mentioned here as a fiict which 

 agrees with our view, that no such pair of muscles is found in Cyphophthalmi, in which 

 operculum genitale is not movable. We agree with de Graaf^ in the view that the pair 

 of muscles in Palpatores (and Cyphophthalmi), which we have marked md on our figures, 

 serve to distend the sheaths round ovipositor, when it is about to be exserted or retracted. 

 Concerning the layer of longitudinal muscle-fibres in Laniatores, Sorensen expressed the 

 view (h, p. 202) that it cooperated with the intersegmental muscles of abdomen in exserting 

 ovipositor, but he had not noticed that a portion of these muscles is bent backwards, as 

 above described — a. fact which renders Sorensen's interpretation of these muscles untenable. 

 On account of this backward turn these muscles can only assist in drawing back ovipositor 



' De Graaf certainly saw both these pairs of muscles, confused them ; m" on his fig. 84 is our md, but on his figures 

 which we have marked vul and me on our figures, but he 85 and 89 m" is our me. 



