PLATE 2 
f EXPLANATION OF FIGURES 
7 and 8 The posterior end of a young specimen of Phoreiobothrium from 
a shark artificially infected with the Scolex polymorphus. These figures show 
the formation, either of psuedo-proglottids which are molted, or an irregular 
beginning of true proglottid formation like that of Crossobothrium laciniatum 
(Curtis, 06). The figure shows so much irregularity that the process does not 
seem lke true proglottid formation and the posterior end shows a peculiar outline 
which probably indicates that part of the specimen has been lost. Only the larger 
pair of the two water trunks is shown. Magnified about 70 diameters. 
9 One of the largest specimens of Phoreiobothrium triloculatum which was 
secured from the artificially infected sharks (see shark no. 8 of table 7). This 
is one of the few specimens which showed a segmentation of the posterior end 
sufficiently regular for comparison with the formation of the posterior proglot- 
tids in Crossobothrium laciniatum. The scolex of the specimen is shown in out- 
line only. The area of the minute spikes is shown and back of this the two pairs 
of water trunks which in such a view are superposed throughout the length of the 
body, are here shown in successive regions. Magnified about 70 diameters. 
10 and 11 Two of the smallest of the specimens of Phoreiobothrium trilocu- 
latum obtained from the artificially infected sharks (see shark no. 3 of table 
7). The specimens represented in fig. 10 was ragged at the posterior end as 
though portions had been detached. Magnified about 70 diameters. 
12 and 13° Show in more detail the features of the Scolex polymorphus. In 
fig. 12 the ‘myzorhynchus’ or proboscis-like structure is shown at the anterior 
end between the four bothria. The larger and smaller water vascular trunks are 
shown in successive regions and their convergence toward the posterior end where 
the vesesls become irregular and branched so that they can only be followed as an 
area of differentiation in the parenchyma. Each bothrium consists of a denser 
portion divided into three regions or loculi in the older specimens (fig. 12), and 
in those slightly smaller often showing only the line of division at the anterior 
end (fig. 13). In fig. 13 the opening of the terminal vesicle of the water tubes is 
seen in surface view, the posterior end of the specimen being slightly turned toward 
the observer. Magnified about 70 diameters. 
