Full resolution (JPEG) - On this page / på denna sida - I. Description of the developed (imaginal) stages of Chordeuma obesum n. g., n. sp.
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In the living or fresh animals probably a great deal of the inner structure
may be observed directly through the transparent cuticle. In adult females preserved
in spirit only part of the genital organs is distinctly seen as a broad stripe of densely
packed eggs on each side, reaching almost from the front end of the head to the
posterior limit of the third thoracic segment; generally more than the middle third
part of the whole breadth of this region of the body is taken up by the egg-stripe.
The foremost rounded end of the latter contains the ovary, the rest is part of the
oviduct, distended by eggs, still unfertilized and without membrane. Specimens stained
and cleared in glycerine, or better in xylol, reveal considerably more of inner structures.
Especially if young, unripe females are used, a fairly complete view of the inner
organisation may be obtained. For sake of control and for further examination
microtome-sections, after imbedding with parafin, have been made. The cuticle,
thick and leathery as it seems to be, is no real obstacle; the tissues are easily stained,
imbibition with parafin and the cutting into sections are performed without difficulty;
in many cases complete series of very thin sections have been obtained. In the same
way males and larval stages have been studied.
Genital organs. (Pl. I, Figs. 8, 9). There are two ovaries (ov), situated in
the head. Each is a lenticular body sending out from its medial margin a short and
narrow transverse branch to connect with the corresponding branch from the opposite
side, thus forming a bridge dorsally across the stomach (if the branches really are
completely fused at their meeting point or a dividing membrane is left here, I have
not made out with certainty). The anterior and medial margins with the bridge
contain small genital cells; the remaining part of the ovary is taken up by
considerably larger egg-cells. From the lateral and posterior part passes out the oviduct (od),
the greater part of which runs straight to the third thoracic segment and is laterally
somewhat compressed; distended with eggs, as in ripe females, its transverse section
is ovoid; when empty, as in unripe females, the shape is more rounded. The epithelium
of this part is almost cubic. In the ripe females the eggs contained in the oviduct
increase in size from before backwards; near the ovary they are only somewhat larger
than those of the ovary; from here and through the head they may be arranged in
two strata, in the thorax according to their size they are arranged in a single
stratum, but in several rows and so densely crammed that their shape is more
angular. In the third thoracic segment the oviduct suddenly narrows for
immediately again to expand into a sausage-shaped terminal part, the epithelium of
which is high and secreting. In the interior of this part I never found any eggs but
more or less of a secretion, staining deeply with hæmatoxyline, carmine (hæmalum)
etc.; the piling up of eggs always ceases at the constriction. Probably the eggs on
being laid pass rapidly through the terminal part, the epithelium of the letter yielding
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