Digenetic Trematodes, I — YAMAGUTI 
475 
TABLE 2 
Comparison of Allonematobothrium with Related Genera 
CHARACTER 
Nemato- 
bothrium 
Allonemato- 
bothrium 
Nemato- 
bothrioides 
Metanemato- 
bothrium 
M etanemato- 
bothrioides 
Neonemato- 
bothrium 
Allometanema- 
tobothrioides 
Body 
encysted in 
pairs 
encysted in 
pairs 
free 
free 
free 
free 
free 
Pharynx 
present 
absent 
present 
rudimentary 
present 
rudimentary 
present 
Esophagus 
simple 
simple 
simple 
simple 
simple 
unusually 
long, 
diverticulate, 
glandular 
very long, 
winding, not 
diverticulate, 
not glandular 
Ceca 
simple 
simple 
simple 
simple 
simple 
very narrow, 
convoluted 
very narrow, 
convoluted 
Acetabulum 
present 
present 
absent 
rudimentary 
present 
absent 
absent 
Testes 
juxtaposed 
juxtaposed 
juxtaposed 
juxtaposed 
obliquely 
tandem 
obliquely 
tandem 
obliquely 
tandem 
Ovary 
undivided 
undivided 
undivided 
divided 
undivided 
undivided 
undivided 
Uterus 
first 
ascending, 
forming 
2 loops 
first 
descending, 
forming 
1 loop 
first 
descending, 
forming 
1 loop 
first 
descending, 
forming 
3 loops 
first 
descending, 
forming 
1 loop 
first 
descending, 
forming 
3 loops 
first 
descending, 
forming 
3 loops 
tremity (0.53 mm in the type, 0.16 mm in one 
entire paratype, from this extremity ) and passes 
imperceptibly into the wide vas efferens which 
runs forward alongside the distal ascending 
uterus and unites with its fellow from the ante- 
rior testis a short distance anterior to the distal 
end of this testis; the vas deferens follows its 
median course all the way through alongside the 
distal uterus and finally opens midventrally to- 
gether with the latter close to the anterior ex- 
tremity a little behind the pharynx. 
Ovary single, tubular, winding, unbranched, 
originating about 8 mm from the head end and 
terminating 2.2 mm from the same point in the 
type, where it is swollen into a pyriform mass 
0.2 mm in diameter; the short germiduct arising 
from the posterior end of this ovarian mass 
soon joins the short ascending vitelline duct 
and leads into the uterine duct; the latter duct 
is at first rather straight but becomes twisted 
as it proceeds backward and is provided with a 
dense coat of shell gland throughout its de- 
scending course; after crossing the median as- 
cending uterus, 3.2 mm behind the ovary in 
the type, it leads into the straight narrow lat- 
eral ascending uterus. This ascending uterus 
turns backward across the ceca, distal ascend- 
ing uterus, vas deferens, and excretory vesicle 
to take a descending course on the other side 
at a distance of 3 mm from the head end in 
the type. The descending uterus turns forward 
across the posterior testis and excretory vesicle 
0.83 mm in the type and 0.24 mm in one entire 
paratype, from the posterior end to be contin- 
ued as a final median ascending uterus, so that 
at a postovarian level there are seen four por- 
tions of the uterus, namely, descending uterine 
duct, proximal ascending, intermediate descend- 
ing, and distal ascending uteri. Eggs bean- 
shaped, 21-26 X 12-16 /x. Seminal receptacle 
very much elongated, extending forward from 
genital junction. Vitelline gland single, tubular, 
winding; originating near posterior extremity, 
1.75 mm in the type and 0.6 mm in one entire 
paratype, from this end; it is straightened out 
distally to form an elongate vitelline reservoir 
about 0.1 mm wide in the type. Excretory ves- 
icle tubular, winding, with almost terminal 
