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The shape of the Nematode, in question, is very divergent from that of the
Spiroptera obtusa (Schneider) found frequently in the stomach of Mus decumanus and
Mus musculus. The latter — especially the female — is short and clumsy, almost
spind le-f o rmed, whereas the Spiroptera neoplastica is thread-formed as a filaria.
When seen by reflected light, the colour is milky white, in a way that less trans-
parent organs as intestine, ovaries become whiter, whereas the rest of the animal
appears less distinctly, the chance support on which it is placed shining through
it. When seen under the microscope in transmitted light it presents itself very
pellucid.
As to dimensions of the two sexes a great difference is found, the femafe
reaches a length of 6 — 8 ctm. sometimes even more, whereas the length of the male
will ver\^ seldom be more than IV2 — 2 ctm. The body has almost the same width
throughout its whole length, being as far as the male is concerned between 110 — 130//.
Young females at the beginning of their maturity have a width of 170 — 200//. In a
a female the length of which measured c. 6 ctm., the width was found to be
326//.
Almost opposite the porus excretorius the body tapers very evenly and quickly
towards the front part, which terminates bluntly in a cone. The hind part of the
body keeps its width until the anus, narrowing then very suddently; the tail has the
shape of a short cone the basal diameter of which is about one third of the height.
This, however, is only the case with the females, whereas in the male the hind part
and the tail have developed into a prominent bursa, the structure of which will be
recorded later on.
The cuticula presents very distinct and fine transverse striæ which makes the
body look almost annulated on its concave sides, according to the movements of the
worm. The thickness of the cuticula almost at the middle of the animal measured
12,6 /« in a female of average size (c. 6 ctm.) 9,4 /« in a female of the length of 3 ctm.
and 6,3 fx in male of average size.
In the front part of the body the cuticula presents most peculiar changes: to-
wards the proximal half of the oesophagus the annulation loses its regular build, and
disappears successively until it is finally replaced by some large vesicular prominences
more or less globular, egg-shaped or sausage-shaped, like those found in Gongylonema
MOLIN (PI. III fig. 17).
These prominences are of unequal size not only according to the different
individuals but within a single worm too. Relatively and absolutely they are most
conspicuous in the bigger females. On contraction of the front part, performed even
by this species to an extraordinary degree, the vesiculæ become more prominent,
whereas on extension they present themselves less distinctly, and almost disappear
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