371] 



PSEUDOPHYLLIDEA FROM FISHES— COOPER 



83 



within cysts in the liver of the intermediate hosts, as recorded by a number of 

 writers, those of T. rohustus are constantly encysted in large numbers in the 

 flesh — Olsson having found them in Coregonus albula and C. lavaretus, Luther 

 (1909:58) in C. albula, and Fuhrmann in the "brochet" (? Esox lucius). 



The scolex of the rohustus type (Figs. 12 and 13) is, as described by Olsson, 

 in the form of a truncated rectangular pyramid, that part immediately behind 

 the terminal disc being considerably constricted and more nearly elliptical 

 in transverse section. As stated by Fuhrmann. "La limite posterieure du 

 scolex de T. rohustus est nettement marquee et les deux bothrias, I'un dorsal 

 I'autre ventral, son tres profonds. ..." This delimitation of the scolex is 

 emphasized by the fact that immediately behind the posterior border of the 

 bothria the dorsal and ventral surfaces of the body of the larva are distinctly 

 concave as are also the lateral surfaces, quite diagrammatically, in fact, as 

 shown in the figures. These concavities extend farther back for a few milli- 

 meters and then gradually flatten out and pass insensibly into the convexities 

 which together form the elliptical outline of the cross-section of the middle 

 of the larva. And it should be emphasized that this was found to be a con- 

 stant feature of all the material studied and not simply due to any possible 

 local collapsing during dehydration. Altho, as shown in the table, the measure- 

 ments of the whole scolex are much smaller than those given by Fuhrmann, 

 as might be expected it is chiefly the structure and size of the trident of hooks 

 that leads the writer to consider this type of larva to belong to T. rohustus. 

 Figure 14 of one of these compares very favorably with those shown in Olsson's 

 figures 31 and 32 and Fuhrmann's figure 2, while the measurements (see table) 

 quite agree with those given by the latter. The base of the trident is com- 

 paratively long or deep (in the sagittal direction), hence the specific name 

 according to Olsson, while not only the full length of the larger hooks but also 

 a good deal of the median ones project thru the cuticula as the functional tips. 

 In figure 14, which is from an alcoholic specimen, these are seen to be darker 

 than the basal piece. The following measurements are given for comparison 

 with Fuhrmann's of adult specimens, which are placed alongside, the data in 

 parentheses being of the opposite trident on the same surface of the scolex in 

 question : 



