LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 665 
being so greatly distended by the mass of yellowish eggs 
that it surrounds and conceals the other organs of the body. 
The body is covered by a transparent cuticle from 0°002 
to 0°003 mm. in thickness, in which are embedded the rather 
broad, flat spines. The striated appearance of the body 
observed in Bucephalus is no longer noticeable. 
The innermost layer of the cuticle stains the more deeply. 
MUSCULATURE. 
The body-wall has the usual muscle layers, composed of 
circular, longitudinal, and diagonal muscle fibres. The 
arrangement of these muscles is best seen in a tangential 
section (fig. 50). 
The circular muscle fibres, although larger than those in 
Bucephalus, are still extremely fine, being only about 0:0005 
mm. in diameter; the longitudinal muscles are somewhat 
larger, varying in diameter from 0:00075 to 0001 mm.; the 
diagonal muscles, of which there are two sets, are about the 
same size as the longitudinal. 
Tue Sucxine Disc. 
The sucking disc opens ventrally at the anterior end of 
the body (fig. 54). The arrangement of the muscles is the 
same as that described by Ziegler (7, p. 548) for G. fim- 
briatum. 
Tue Digestive Tract. 
The mouth opens on the ventral surface in the anterior 
half of the body. It is succeeded by a short pre-pharynx, 
which passes into the pharynx. This is similar, except in 
size, to that of Bucephalus. ‘lhe muscles are much larger 
than in the cercaria; the ring muscles are oval in cross 
section, about 0°002 mm. long and 0-001 mm, wide. The 
radial muscles are spindle-shaped, about 0°001 mm. in 
diameter in their thickest part (fig. 53). 
The pharynx is followed by the esophagus, the walls of 
