chap, vi.] CESTODA. 169 



122. Even in the groups whose segmentation is commonly perfect, 

 variations in the degree of separation between the proglottides 

 are not rare. It frequently happens that specimens of Taenia 

 are found in which the external segmentation is partial, being 

 only found on half of the contour. This abnormality, which 

 does not affect the internal organs, occurs several times in the 

 same chain. Moniez, R., Bull. Sci. du Nord, x., p. 200. 



123. Taenia saginata. Cases of the "intercalation" of a triangular, 

 wedge-like segment between two proglottides are recorded. In 

 such cases the generative opening is on the same side as in an 

 adjacent segment, not taking part in the alternation. L., p. 572. 

 Compare with similar phenomena in Chsetopoda (p. 156). 



The evidence of abnormal repetition of parts occurring in 

 single proglottides bears on the question of the relationship of 

 the perfectly segmented forms to the less fully segmented. 

 124 Taenia saginata: a specimen 128 mm. long, wanting the 

 head, without any division into segments. The longitudinal 

 vessels were seen, but no transverse vessels were discovered. On 

 the margins were numerous genital openings, of which 41 were 

 counted, each leading from a genital organ. There was no regular 

 lateral alternation between the genital papillae, but they were 

 disposed without uniformity of pattern, and several were closely 

 approximated to each other. In no part was there any trace of 

 division into proglottides. From the characters of the genital 

 openings and from the number and size of the calcareous bodies 

 together with other histological details, the specimen was deter- 

 mined without much doubt as Tcenia saginata. Grobben, C, 

 Verh, zool.-bot. Ges. Wien, 1887, Bd. xxxvu., p. 679, fig. 



Such repetition of the generative openings in single segments 

 is very common, especially in Tcenia saginata, and indeed examples 

 of it may be seen in most chains of segments. Usually such 

 repetition is confined to one segment and is not striking. Five 

 generative papillae have been seen by L. in one segment, and 

 Colin [ref. not found, W. B.] described 25 — 30 genital pores in 

 an unsegmented piece measuring 15 cm. L , p. 571. 



125. Repetitions are not confined to the generative openings, but 

 the generative organs themselves are also thus abnormally re- 

 peated. In cases in which several sets of generative organs occur 

 in the same segment it is found that those near the middle of 

 the segment are the least developed. In these cases, though 

 the different organs frequently cross each other, Leuckart found 

 no anastomoses between them, but the number of distinct sets 

 of generative organs was the same as the number of pores. 



It was not found that the length of the segments increased 

 in the same ratio as the number of the pores they contain. For 

 example, a segment with two pores measured 18 mm. in length 



