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Heligmosomum muris Yokogawa 
the region of the oesophagus to the posterior end. In the anterior region of 
the body three to four small highly refractile specks, like spines, are found 
on the surface of the cuticula at the region about the middle part of the 
oesophagus. Similar structures are recognizable in the tail region. 
Subcuticle and musculature. It is difficult to understand the details of the 
structure of subcuticle and muscle layers in the optical sections of the living 
larvae. However, the lateral bands can be distinguished easily as two longi¬ 
tudinal strands at the sides of the body, since they are more transparent than 
the two neighbouring muscular areas. The dorsal and the ventral bands are 
not clearly distinguished. 
The buccal-cavity . The buccal-cavity is narrower and shorter than in the 
larvae in the first stage. Its structure is shown in Text-fig. 1 a. 
Text-fig. 1. Structures of anterior end. a, Mature free-living larva; b, adult. 
Oesophagus. The oesophagus is more or less claviform in shape and a little 
more slender than in the previous stage. Its lumen appears as a straight line. 
At the posterior end of the oesophagus there are three pairs of clear cells, 
each containing a vesicular nucleus (Fig. 6, eg, Plate VIII). These cells seem to 
correspond to the “oesophageal glands” described by Looss (1911) for the 
hookworm larva. They first become visible in larvae which have completed 
their metamorphosis. 
The intestine. The intestinal lumen is very wide and contains a certain 
quantity of fine granules. The intestinal wall is composed as described above 
of two rows of eight flat cells, each containing an ellipsoidal nucleus. The 
protoplasm of these cells has increased somewhat in thickness over the con¬ 
dition just after the division of the cells. They have a uniform thickness along 
the whole length of the intestine. The nuclei in the cells are sometimes difficult 
to find, being covered by pigment granules. 
Nervous system. The oesophageal ring is more clearly defined and has the 
same position as in the first stage. Details of the structure of the nervous 
system are difficult to make out in the living specimens. 
The excretory system. In the mature larvae, the cervical glands become 
clearly recognizable by their large transparent ellipsoidal nuclei (Fig. 6, ncg, 
