413] PSEUDOPHYLLIDEA FROM FISHES— COOPER 125 



and elongate oval in lateral view, the greatest depth being near the posterior 

 end. They are separated by a prominent lateral groove on each side, which 

 extends from the anterior edge of the first segment to a dorsoventral groove 

 just behind the disc. The latter itself is deeply notched dorsally and ventrally 

 and on account of this groove quite prominent laterally. It is thus seen that 

 the walls of the bothria are com.paratively thin. During life they are quite 

 mobile, as might be concluded from their general appearance as well as from 

 their anatomy. Altho the greatest dorsoventral diameter of both the cavity 

 and the walls is in the posterior portion of the bothrium, the more functional 

 portion would seem to be the a.nterior part immediately behind the notch of 

 the terminal disc. On account of its powerful musculature the disc evidently 

 greatly assists the relatively thicker walls of the bothria in that region in 

 forming a m.ore powerful organ of adhesion than posteriorly. The thin walls 

 behind would, on the other hand, better assist the sagittal musculature in 

 maintaining suction by presenting a greater surface internally for apphcation 

 to the mucosa of the host's intestine. The measurements of the organ are 

 given in the table below. 



The first segments are subcuneate in outline, and show subdivision in a 

 manner similar to that of B. scorpii. Each primary segment is divided into 

 two segments of the second order (Fig. 24), and farther back these in turn into 

 segments of the third order, and so on, until in the region where the reproduc- 

 tive rudiments appear the primary segment contains thirty-two subsegments. 

 This plan can be followed as in B. scorpii even into the region of differentiation, 

 and indeed much more readily since there is much less irregularity due to inter- 

 calated segments and the further subdivision of others. Furthermore, the 

 same sort of dominance of the anterior end of the primary, secondary, tertiary 

 and quaternary segments — that is, until a group of four reproductive rudiments 

 can be recognized — is seen not only in the size of the subdivisions but especially 

 in the first portion of the region "of differentiation, in the rate of differentiation 

 of the common rudiment into the different proximal organs of the reproductive 

 system. As soon, however, as the lumina of the uterus-sacs appear, the plan 

 becomes obscured by the gradual enlargement of the posterior borders of the 

 subsegments, even to those of the fifth order. Thus, in turn there may be seen 

 defined, as one follows them backward, groupings of thirty-two, sixteen, eight, 

 four and two sets of genitalia. Eventually, at the posterior end of medium 

 sized strobilas and for considerable stretches of the largest these pairs become 

 separated, so that the segment contains only one set of reproductive organs. 

 These hindermost segments are usually about four and a half times as broad as 

 long, but in the most relaxed strobilas they may be only twice as broad as long. 

 The ripe segments in some cases may be so much elongated and constricted at 

 their ends that they appear barrel-shaped. This accounts for the apparent 

 discrepancy in the measurements of the third and fourth specimens of the table 

 below. As shown (Figs. 25, 69) the anterior part of the strobila has a dorsoven- 

 tral diameter almost as great as the transverse one — as a matter of fact some 

 parts of the segments are here almost spherical in cross-section — while the 



