146 ILLINOIS BIOLOGICAL MONOGRAPHS [434 



learned that his suspicions were well founded; for D. laciniatum proved to be 

 identical v/ith B. manubriforrais. The posterior segments "with breadth one 

 and a half times the length" had different proportions from those observed in 

 mature material of the latter species, because they were, altho gravid, of quite 

 youngers trobilas. The material of No. 4741 is, in fact, intermediate between 

 No. 4711 of B. manuhriformis and the 16.461 of the same species dealt with 

 above, not so much in size since it does not show the regions so well, as in degree 

 of maturity. The fact that " the segments are not uniform; one segment with 

 a salient posterior border followed by about two with less salient borders" is 

 due to the irregular manner in which the primary segment divides into sub- 

 segments. The dimensions of the eggs correspond, while the measurements 

 of the cirrus-bulb, vaginal sphincter and calcareous bodies are the same in the 

 two species. Linton stated that in D. laciniatuni "The reproductive cloacae 

 lie along the median line of one of the flat surfaces of the body. The external 

 openings of the uterus He along the median hne of the opposite surface. " While 

 the former was found to be the case, the latter was not, for the openings of the 

 uteri lie iirregularly on either side of the median line as in B. manubriformis. 

 Furthermore, the cirrus-bulb was not found to have "its inner end deflected 

 to the right [left, when we take into consideration the fact that the common 

 genital cloaca of D. laciniatuni was considered to open on the ventral instead 

 of the dorsal surface] where it communicates with the vas deferens, which 

 lies in numerous folds in front and to the right of the cirrus-bulb," but to 

 alternate irregularly from side to side according as the uterus-sac and distal 

 end of the uterine duct occupy the other side of the proglottis; while the vas 

 deferens was as described above (p. 142). Altho the vaginal bulb was found 

 to be a little larger in the material of D. laciniatum, its structure and position 

 were also quite as in B. manubriformis. On the other hand no muscle fibres 

 completely encircUng both genital apertures, such as shown in Linton's Fig. 

 5, PI. XXXI, were seen, but what might easily be taken for such were formed 

 by the crossing of much curved and spread longitudinal and transverse fibres 

 of the body wall, in such a manner that the portions intersecting at the four 

 comers run in almost circular directions and concentrically parallel to each 

 other so as to give the appearance of the whole forming a complete ring in each 

 case. The genital cloaca was found to be shallower than in the material from 

 Histiophorus gladius. This is evidently due to the fact that the proglottides 

 were younger and not yet gravid as in those from the latter host. The uterus- 

 opening was not found to be "lined with cilia" but with irregular ragged 

 processes which are evidently only portions of the lining of the developing fun- 

 nel and the external duct of the same. Finally the position and structure of 

 the ovary, of the vitelline reservoir and of the various layers of the body 

 exactly correspond in the two forms. 



Consequently the writer feels that there can be no doubt whatever concern- 

 ing the identity of D. laciniatum with B. 'manubriformis, which fact also seems 

 to be recognized in the Fauna of the Woods Hole Region (Sumner, Osbom 

 and Cole, 1913: 585) where the former is not found among the cestodes, altho 



