TJie Anatomy of Opisthopatus cinctipes. 75 



longer and often 'extend beyond the adjoining pair to the bases of 

 the second nearest pair of legs. Only a small part of the pouch is 

 situated within the cavity of the leg itself. The course within the 

 leg is shown in fig. 26, in which the gland passes first upwards and 

 then inwards until it comes into contact with the dorso-ventral 

 muscular septum {dvs) separating the mesial from the lateral 

 sinuses. Here it bends abruptly forwards or backwards and runs 

 along the upper side of the nerve cord in the lateral sinus. Opposite 

 the cavity of the legs the gland lies in the triangular space situated 

 between the nerve cord and the two dorso-ventral muscular septa, 

 represented in the left side of fig. 25 {dvs and dvs ^) and also 

 indicated in fig. 26. 



The duct is distinctly marked off from the tubular pouch, being 

 much thinner than the latter, and it lies wholly within the leg 

 cavity. Its walls are composed of a simple epithelium with small 

 nuclei, and its inner contour is very sharp and distinct, apparently 

 owing to the presence of a fine cuticula (fig. 26). 



The wall of the tubular pouch, on the other hand, is an epithelium 

 composed of large glandular cells about as high as thick and 

 furnished with much larger nuclei. Within the pouch portions of 

 coagulated secretion may be observed. A thin cellular layer, with 

 small flattened nuclei, envelopes both pouch and duct, representing 

 muscular and perhaps peritoneal cells. 



The arrangement by which the ducts open exteriorly is peculiar, 

 and may be best seen externally in drowned specimens, such as is 

 represented in fig. 14. Bordering the distal half of the hind margin 

 of the coxal organ {ex) in the 6th to 13th pairs of legs a large, bright 

 brick-red and therefore very conspicuous fold of skin is observed, 

 forming a ring-shaped tumid lip (r./) round an opening. Owing 

 to transverse constrictions the ring-fold appears as if composed of 

 several separate tubercles, although in reality this is not the case. 

 In the centre of a well-expanded ring-fold a large papilla may be 

 observed, at the apex of which the duct of the crural gland opens. 

 The papilla is only distinctly visible when its apex projects up to or 

 beyond the level of the summit of the ring-fold, but in many cases 

 when it is withdrawn below this level the papilla becomes externally 

 invisible owing to the contraction of the ring-fold. 



In the living animal the ring-fold and papilla may be readily 

 observed in the conditions just described, and I even saw the 

 central papilla protruded from the opening and again withdrawn 

 on one occasion. Both ring-fold and papilla may, moreover, be 

 completely withdrawn, apparently at the will of the animal, into the 



