326 ' LEWIS HENRY GOUGH. 



acquisition of a psendo-scolex. A fundamental difference 

 is, however, that in Stilesia all segments must have passed 

 through the pseudo-neck during the course of their develop- 

 ment, whereas it is usually accepted that a true pseudo-scolex 

 is formed after the fertile segments have been produced, and 

 that the segments composing a pseudo-scolex remain sterile. 

 The habit of contracting the youngest segments appears to 

 be an old acquisition in tlie genus Stilesia ; a scolex of 

 Stilesia gl obipu nctata (Rivolta), is illustrated in fig. 12, 

 showing a similar contraction of the anterior portion of the 

 strobila, though in a less degree. 



The segments are much shorter than wide, and about twice 

 as wide as thick. The width of the strobila varies from one 

 to two or three millimetres. The posterior segments are 

 longer than the anterior. The posterior margin of each 

 segment surrounds, collai'-like, the anterior end of the 

 following, except at the middle of the segment. Segmenta- 

 tion is quite distinct (without sectioning) at 2*8 mm. from 

 the scolex; the genital anlagou appear already at 9 mm. 



The genital pores open near the middle of the lateral 

 margin of the segment ; they are single and irregularly 

 alternate. 



The cuticula does not appear smooth (as that of Avitel- 

 lina centripunctata [Rivolta,]), but is villous (in sections). 



The longitudinal canals are both well developed. The 

 lumen of the dorsal canal does not become obliterated. The 

 ventral canal is situated lateral and ventral to the dorsal 

 canal. At the posterior end of each segment transverse 

 canals connect the ventral canals, forming a transverse ring, 

 the dorsal and ventral branches forming a few anastomoses 

 near the middle of the segment. The transverse canals arise 

 from more than two, usually three or four openings in the 

 ventral canal on its median side, and two or three lateral to 

 the ventral canal ; these last usually meet and form a lateral 

 loop. The histology of the transverse canals is the same as 

 of the ventral canal. They both have a thin membrane, 

 produced by flat epithelial cells, surrounding the canal ; these 



