LIFE HISTORY OF A TROUT PARASITE. 
357 
EXPLANATION OP FIGURES. 
The following letters have the same significance in relation to all the figures where they are used. 
c. cuticle. 
6. bothrium, 
l.m. longitudinal muscles. 
c. m. circular muscles. 
/. V. fibro-vascular layer. 
Drawings by the author. 
p. V. peripheral vessels. 
m. V. marginal vessel. 
a. V. aquiferous vessel. 
vit, vitellaria. 
o. ovary. 
Plate CXVII. 
ov. ova. 
P. cirrus. 
P'. cirrus bulb. 
d. vas deferens. 
t. testes. 
Figs. 1 to 14. Larval stage of Dibothrium cordiceps Leidy, from peritoneal cavity and muscular tissues 
of the trout {Salmo mykiss). 
Fig. 1. Sketch of head from life, marginal view, lateral of body, from muscular tissue of host ; after 
lying in water three or four hours this specimen measured 34 centimeters in length and 
2.5 millimeters in breadth, nearly linear, X about 12. 
Fig. 2. Head of specimen from flesh of host, marginal view of head, lateral of body, alcoholic, X 
about 12. 
Fig. 3. Same view of another specimen, alcoholic, X about 12. Lateral view of same specimen 
shown in Fig. 8. 
Fig. 4, 5, and 6. Sketches from life showing some of the diverse shapes assumed by the head and neck 
of a living worm, each magnified about 12 linear diameters. 
Fig. 7. Head and neck of an alcoholic specimen, X about 12. 
Fig. 8. Lateral view of head, marginal of neck, same specimen as sketched in Fig. 3, X 12. 
Fig. 9. Lateral view of head, marginal of neck; large specimen, 35 centimeters in length, from flesh 
of host, alcoholic, X 12. 
Fig. 10. Median segment of same specimen, X 12. 
Fig. 11. Anastomosing vessels of water-vascular system, middle of body, compressed, sketch from life. 
Pig. 12. Water- vascular system, posterior end of large specimen, compressed, sketch from life. 
Fig. 13. Posterior end of another smaller specimen, compressed, sketched from life ; a, pulsating ves- 
sel; t.p., terminal pore. 
Fig. 14. Posterior end of large specimen, alcoholic, X 12. The emargination is sometimes deeper 
and sometimes not so deep as this. 
Figs. 15 to 34. Adult stage of Dibothrium cordiceps Leidy, from intestine of the white pelican (Pele- 
canus erythrorhynchus). 
Figs. 15, 16. Marginal view of head, lateral of neck of two different alcoholic specimens, X about 
15 and 24, respectively. 
Plate CXVIII. 
(Adult stage of Dibothrium cordiceps Leidy, intestine of white pelican.) 
Fig. 17. Marginal view of head, lateral of neck, alcoholic, X about 24. Same specimen as shown in 
next figure. 
Fig. 18. Lateral view of head of specimen figured in No. 17. 
Fig. 19. Lateral view of head of another specimen, X 15, alcoholic. 
Fig. 20. Segments of body towards anterior end, alcoholic, ventral surface, x 
Fig. 21. Antero-median segments, ruffled margin, dorsal surface, alcoholic, X 4. 
Fig. 22. Median segments of small fragments, alcoholic, X 12. 
Fig. 23. Mature segments from large specimen, alcoholic, X about 5. 
