LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 689 
Fic. 32.—Transverse section of one of the tails of Bucephalus. 
Fic. 33.—Longitudinal section taken slightly on one side of the median 
line of one of the tails of Bucephalus. 
Fic. 34.—Horizontal section of the middle piece of the tail of an immature 
Bucephalus. 
Fic. 35.—Transverse section through the anterior end of Bucephalus. 
Fie. 36.—Transverse section through the anterior end of Bucephalus, 
slightly posterior to that shown in Fig. 35. 
Fic. 37.—Transverse section through immature Bucephalus; cuticle not 
yet formed. 
Fie. 38.—Transverse section through immature Bucephalus in region of 
pharynx; cuticle not yet formed. 
Fic. 39.—The water vascular system of Bucephalus. Somewhat diagram- 
matic.. Drawn from sections and from living specimens stained with methy- 
lene blue. 
Fie. 40.—Section through shell glands of Gasterostomum graci- 
lescens. 
PLATE 41. 
Fie. 41.—Dorso-ventral longitudinal section through nearly mature Buce- 
phalus. The cercaria was slightly bent, so that the section is median from 
the mouth to the anterior end, and oblique posterior to the mouth. For 
median section of posterior end see Fig. 25. 
Fie. 42.—Longitudinal section of portion of body wall of Bucephalus. 
Fic. 43.—Horizontal longitudinal section of Bucephalus, showing brain 
and lateral nerves. 
Fic. 44.—Section through a vitellarium of Gasterostomum graci- 
lescens. 
Fic. 45.—Transverse section through penis of Gasterostomum graci- 
lescens. 
Fie. 46.—Gasterostomum gracilescens in ventral view. R. Right. 
Fic. 47.—Gasterostomum gracilescens in dorsal view. R. Right. 
Figs. 46 and 47 are somewhat diagrammatic. ‘The spines are not shown. 
Sketches were made from living specimens. After study cf sections, details, 
which it had been impossible to make out in the whole mounts, were added. 
Fie. 48.—Encysted form found in Menidia menidia. 
Fic. 49.—Young Gasterostomum gracilescens found in Menidia 
menidia and in experiment fish at conclusion of feeding experiments, 
