456 MALFORMATIONS OF T/ENIA SAGIXATA. 



together by projecting ridges. At the point where they were fused, 

 at the apex of the pyramid or thereabouts, there were two sexual 

 papillae generally closely approximated. 



At first sight these structures are, as we have said, extremely 

 puzzling, but on closer examination one becomes convinced that they 

 are proglottides in which the prismatic character is combined with a 

 multiplication of the generative papillae. They represent, in other 

 words, two imperfectly separated prismatic proglottides of asym- 

 metrical arrangement. 



FIG. 262. Prismatic proglottides with double porus genitalis ; A -C from 

 the front, D ( = same specimen as O from behind (nat. size). 



The three side walls, although superficially very like one another, 

 are in reality different, since two of them are halves of a sym- 

 metrical structure, like the two usual wings, while the third seems 

 to be a wedge-like piece which is intercalated into the triangular 

 space left by the posterior borders of the other two. We may then 

 explain the arrangement of the generative papillae by supposing that 

 one belongs to the lower end of the longitudinal ridge which runs 

 between the shortened wings, while the other is united to the 

 lower wedge-like portion which is always connected with one of the 

 wings, sometimes with the left and sometimes with the right. The 

 seam between these two parts denotes the anterior border of the wedge- 

 like piece, and the free border of the latter turned towards the other 

 wing is, in spite of its marked contraction, to be regarded as the 

 lateral border. This is in harmony with, the fact that the latter bears 

 the second genital papilla high up, close behind the longitudinal 

 ridge. This margin is succeeded by one inclined to it at an angle, 

 and directed somewhat laterally owing to its contraction, but repre- 

 senting the posterior border, as is proved by its projecting and everted 

 margin into which the succeeding joint fits. 



Subsequently I found another proglottis which demonstrated the 

 truth of the above representation, inasmuch as it exhibited a stage 

 perfectly intermediate between the ordinary prismatic structure and 

 the one just described. It showed quite undeniably (Fig. 262, A) 

 the two ordinary lateral wings and the longitudinal ridge, but differed 

 in that the former were somewhat shorter than usual, and bore the 



