1909. ] THREAD-WORMS OF THE RED GROUSE. 347 
usually a dark granulation which serves very clearly to define 
their limits (Pl. LIV. fig. 35). 
The lumen of the cesophagus which pierces these peculiar cells 
is very minute, and is lined with a definite chitinous tube, The 
“cellular body,” as the aggregate of the cesophageal cells is some- 
times called, ends abruptly, about one-fifth the body-length from 
the anterior end. Here the cesophagus passes quite abruptly into 
the capacious intestine with its many-celled wails. Just at this 
point, and tucked away in the angle formed by the minute 
esophagus widening into the broad intestine, are a couple of 
glands, probably the homologues of the cervical glands of other 
nematodes (Pl. LIV. fig. 38). The intestine continues to the 
hinder end of the body with no change; it is somewhat difficult 
to distinguish, as it is just about the same brown colour as the 
lateral lines. The posterior end of the female is truncated and 
the anus is at the ventral side of the abruptly terminated body. 
The ovary is a single tube which anteriorly contains undif- 
ferentiated eggs. These gradually attain a definite and somewhat 
irregular outhne. Posteriorly the ovary opens into a spacious 
uterus, in which the ova are oval, with a distinct vitelline mem- 
brane. The uterus is broad, and serves, with its contents, to 
conceal the other organs of the body. Posteriorly, where the 
body is wide, the ova are irregularly crowded together; there 
may be as many as five or six ova in a transverse row. Further 
towards the head the ova acquire their characteristic egg-shell 
with two bright spotsateach end. They closely resemble the eggs 
of Trichocephalus trichiurus (dispar) (.) (Pl. LIV. figs. 40 & 41). 
About halfway along the body the diameter lessens as we pass 
forward, and after a certain space the uterus is narrowed and only 
permits a couple of eggs to be abreast, and finally the eggs are 
reduced to a single row. ‘The uterus opens by a vagina which is 
situated a little way behind the end of the “ cellular body,” ¢.e. just 
behind the anterior end of the intestine. The uterus or vagina 
is usually prolapsed and forms a bell-like structure, one edge 
of which usually has a clear oval vesicle in its walls (BE Tein 
fig. 38). Through this bell-shaped structure the eggs pass out. 
“The male is markedly smaller than the female, Its average 
length is about 25 mm. and its width throughout does not surpass 
the anterior end of the female’s body. 
The testis is a single tube which opens posteriorly. At the 
tail end the male has a pair of cuticular folds or flanges, possibly 
representing a genital bursa. There is a single spicule, very 
long, and in many cases only perhaps protruded for a fourth or 
fifth of its whole length. It is described as having a sheath, but 
in the specimens we have seen this was not appar ent—probably it 
was retracted (Pl. LIV. fig. 39). 
The males are very much rarer than the females—in fact, we 
examined a considerable number of specimens without finding a 
single male, probably they occur in about the proportion of one 
to seven or ten females. We have occasionally found a very 
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