A NEW SPECIES OF PENTASTOMXJM. 175 



This is the external opening of an annular groove, whose depth is generally 

 about equal to the diameter of the circle, though it is sometimes a little deeper. 

 The two sides of the groove are almost in contact, so that its breadth is quite 

 infinitesimal. 



From this it follows that the papilla, which is separated by the groove from 

 the surrounding tissues, is a short cylinder, of about equal length and diameter. 

 It is not quite regular in form, however, but the base is a little contracted from 

 side to side, while the antero-external angle is sometimes a little rounded off 

 (PI. XXVII. fig. 8). 



The cuticle which covers the free extremity of the papilla is not to be dis- 

 tinguished from that covering the remainder of the body, while that upon the 

 sides of the groove is a little thicker, and absorbs the staining material (heemat- 

 oxylin) more greedily, and is provided with a number of small spines (fig. 4). 



The subcuticular epithelium of this organ presents no note worthy of modifi- 

 cations, but its muscles are rather complex, and indicate that it is an organ of 

 considerable functional activity. 



The papilla itself contains two (possibly three) sets of muscular fibres — the 

 first traverses it almost parallel to the longitudinal axis of the body, slightly 

 approaching the ventral surface as it passes backwards (PI. XXVII. fig. 8) ; 

 the second passes from its base towards the free extremity, bending slightly 

 inwards as it proceeds. Some of the sections of the papilla seemed to show 

 a thin marginal layer of fibres, divided transversely, which would of course 

 constitute a sphincter, but these appearances were so uncertain, that I do not 

 feel justified in doing more than merely alluding to them. 



In addition to these, a clearly-defined retractor bundle runs obliquely for- 

 wards from the middle of the body into the papilla (PL XXVII. fig. 8), while 

 all around it slender groups of fibres pass outwards, and are inserted into the 

 cuticle. 



From a consideration of the structures above described, it seems probable that 

 this papilla can be protruded after the manner of a proboscis ; the last named 

 muscles being specially efficacious in assisting this action ; the subsequent retrac- 

 tion also is amply provided for. Furthermore, the intra-papillary antero-posterio 

 fibres will, by their contraction, increase the space behind the papilla, which 

 the retraction and consequent swelling of this latter will again diminish, thus 

 obviously aiding the operation of deglutition. A third function possible to this 

 organ is that of a sucker, to secure the adhesion of the parasite to its host. 



No structure of this kind would appear to exist in L. tamioides, whose 

 mouth is merely " a widely gaping orifice " (eine grosse und klaffende 

 Oeffnung), # followed by a funnel-shaped pharynx, along which the chitinous 

 lining is continued as far as the stomach itself. 



* Leuckart, loc. cit. p. 55. 



