F. H. Stewart 
387 
ring is prominent (fig. 7) lying slightly behind the junction of the anterior 
and middle third of the oesophagus. The excretory pore lies immediately 
behind the nerve ring. The nucleus of the excretory cell is a large and 
prominent body lying between the left lateral line and the oesophagus at 
the junction of the middle and posterior third of the latter organ (figs. G and 7). 
The rudiment of the gonads is situated just behind the middle of the 
body length (fig. 8). It consists of two rudimentary tubes leading backward 
to a rudimentary external aperture in the ventral line. The outline of the tail 
is shown in fig. 9. 
These larvae have therefore reached a more advanced stage than the 
specimens from the trachea. An ecdysis has doubtless occurred between the 
two stages. 
Measurements of a specimen mounted in Canada balsam: total length 
2-4 mm. Head to nerve ring 0-126 mm. Head to excretory pore 0-144 mm. 
Head to end of oesophagus 0-324 mm. Head to rudimentary sexual aperture 
1-638 mm. Length of tail 0-0828 mm. 
EXPLANATION OF PLATE XX. 
Fig. 1. Outline of larva, x 80. 
Fig. 2. The head, x 800. 
Fig. 3. Transverse section through the lips, and oblique longitudinal section through the body 
wall at about the middle of -the body length, x 800. 
Fig. 4. Transverse section through the head immediately behind the lips, x 800. 
Fig. 5. Transverse section immediately behind the nerve ring, x 800. 
Fig. 6. Transverse section at the level of the nucleus of the excretory cell, x 800. 
Fig. 7. The oesophageal region, x 320. 
Fig. 8. The gonads, x 800. 
Fig. 9. Outline of the tail, x 800. 
Lettering: an., anus, b.d.l., base of dorsal lip. b.l.s.v.l., base of left subventral lip. c.r., ring in 
cuticle of body surface. D., dorsal, d.l., dorsal line, g.a., genital aperture, go., gonad. 
gr., groove on internal aspect of lip. Int., intestine. 1., lip. I.I., lateral line, l.m., lateral 
membrane, m., longitudinal muscular band, mus., muscular bundle of lip. n.e.c., nucleus 
of excretory cell, n.r., nerve ring, oes., oesophagus, pap., papilla, sk., skeletal support of 
lateral line. V., ventral, v.l., ventral line. 
