481] PSEUDOPHYLLIDEA PROM PISHES— COOPER 193 



the worms from the salmon. In the latter the segments, as shown in figure 

 39, are at first short and broadly cuneate and at once become still shorter 

 and more crowded. On the whole the marine form of the species appears to be 

 constantly in a better state of nutrition than the fresh-water form. As the 

 measurements given here indicate, the strobila is much wider and thicker and 

 the scolex much larger; but what attracts one's attention at first sight is the 

 clear-cut nature of the scolex and segments of this, the prohoscideus type, which 

 led BelUngham (1844:252) to describe it as "a very beautiful species," as 

 compared to the other form. In the latter the posterior, much-crowded pro- 

 glottides, especially, are often irregularly swollen transversely or longitudinally 

 bo as to present appearances in many cases quite like those to be seen in A. 

 rugosum. Much of this may, however, be due to osmotic action when the 

 worms are near the point of death with the possible low resistance of the body- 

 wall of the posterior segments when growth and development have gone on to 

 such a stage that they are little more than sacs filled with eggs. As pointed 

 out by various writers the posterior borders of the segments are provided in 

 the median line and on both surfaces with a distinct notch or emargination, 

 which together form a longitudinal groove on each face of the chain. This 

 is quite pronounced in the strobilas from the salmon but often not so marked 

 in those from the whitefish, lake trout and ling. In these it is confined 

 more to the posterior stretches of the segments and greatly exaggerated by 

 the above mentioned irregular swellings which, however, do not cross the longi- 

 tudinal groove formed by these notches. Often this groove may be present 

 in the segments close to the scolex and agam in posterior ones but absent in 

 the middle stretches, where, of course, the emarginations are either almost 

 ♦ibsent or all but obUterated by the degree of relaxation. On the contrary, 

 Olsson (1893:17) often found the groove only in the middle portions of the 

 infundibuliformis form. Many specimens also show the condition described 

 by Leuckart (1819:42) w^hen he said, "Die hinteren Rander dieser GUeder 

 scheinen allerdings etwas verdickt und stehen an den Korperrandem sehr 

 hervor. " In the anterior segments of considerably relaxed or especially young 

 strobilas something of the manner of segmentation can be seen. This was 

 found to take place much as in the genus Bothriocephalus, altho the writer 

 was not able to distinguish the primary segments to his satisfaction. What 

 was considered to be such is shown in figure 64, a sketch of segments beginning 

 27mm. from the anterior end of the strobila in question. The idea of domi- 

 nance of the anterior portions over the posterior portions in segmentation, 

 as brought out under B. scorpii, is here shown very nicely. In the prohoscideus 

 type of strobila the same method of subdivision was followed in the anterior 

 segments, altho with greater diflSculty on account of the fact that the segments 

 are so closely crowded in the longitudinal direction. Olsson (1867 :53) noticed 

 the subdivision of the segments producing an alternation of larger segments 

 with smaller ones, and he considered it to be an artictdatio spuria similar to 

 that described by Wagener (1854:69) for Amphicotyle hetero pleura and by 

 Krabbe (1865:384) for B. scorpii and other species. Later Olsson (1893:17) 



