TAPE-WORMS OF THE SUB-FAMILY AVITELLININ.E. 325 



As one very rarely succeeds iti extracting a worm entire 

 its total length is very difficult to estimate, but it is probably 

 between twenty and fifty centimetres. In life, when expanded, 

 it is thin, gelatinous in appearance, semi-transparent, the 

 edges of the strobila being serrated on account of the pi-o- 

 jection of the posterior angles of the segments. Against a 

 black surface, the middle field appears clear, the lateral fields 

 more or less opaque. In older segments in the posterior 

 portion of the strobila, the uteri and paruterine organs show 

 up as an opaque spot on each side of each proglottid ; when 

 contracted, the worm is thick, with frilled edges, and more or 

 less opaque. 



The scolex has four suckers, directed outwards and 

 forwards. Very frequently the head is followed by what 

 appears to be a thick " neck," 2 mm. in length, as broad as, 

 or even slightly broader, than the scolex ; behind this " neck " 

 the strobila suddenly narrows to half the width. Exami- 

 nations of the "neck" (in sections), however, reveals the 

 fact that it is composed of youug segments, and consequently 

 belongs to the strobila and not to the scolex. The contrac- 

 tion of the first two millimetres of the strobila is of extremely 

 regular occurrence, so much so as to cause remark, when one, 

 as occasionally happens, comes across a worm not contracted 

 in this way. As the scolex is usually lodged in a capillary 

 of the bile-duct the swelling of the anterior portion of the 

 strobila can be of use to the worm as an aid to the suckers, 

 helping to anchor the worm by gripping the sides of the 

 duct. Wolffhiigel figures a scolex in his paper, which he 

 states may belong to Stilesia hepatica; although the 

 scolex in question is not followed by the contraction of the 

 anterior portion of the strobila, I see no reason to doubt 

 its belonging to this species. 



The swelling of the portion of the strobila directly posterior 

 to the scolex in Stilesia hepatica, Wolffhiigel, on 

 account of its probable function, can probably be compared 

 to the pseudo-scolices of Idiogenes and Fimbriaria, and 

 be considered as representing the first step towards the 



