Medical Officers of the Army of India.
11
measure about 1/80" (0.34 mm.) in length by rather less than 1/1000" (0.025 mm.) in
diameter. Although I have frequently examined embryos just escaped from the egg,
I could never make out any pulsatile action of the pharyngeal bulb, such as is seen
in all the embryos of Dochmius duodenalis, but only irregular slow contractions of
the pharynx. They grow with great rapidity, so that in a few hours they have
attained a length of 1/50" (0.5 mm.), and have increased considerably in thickness.
By this time the outlines of the internal organs have become distinct, the intestine
being marked out as a distinct granular mass, between the lining cells of which
the lumen of the tube pursues the serpentine course characteristic of young ne-
matodes. A relatively large share of the body length is taken up by the pharynx
and its bulb, a third of the body proper being so occupied, the pharynx being
exceptionally wide and strong, and rather widening out at its aboral end
than forming a distinct bulb. The portion of the body length occupied by the
intestine proper is relatively short, only exceeding that of the pharyngeal portion
by about 1/800" (0.034 mm.), the anus being placed rather far forward, so that the
intestine does not extend into the long tapering tail. They change skin frequently,
and any specimen containing many of them will be sure to exhibt a considerable
number engaged in the process of getting rid of their old integuments, the
long empty chitinous tube, still attached, giving rise to all sorts of queer
appearances.
The development of the generative organ's and of the lemniscus is exactly
similar to that of Dochmius duodenalis; so that to enter into the details of the
process would necessarily be merely a repetition of the description of the
development of the Rhabditis of that parasite given in my recent "Report on
the diseases known in Assam as Kala azar, and Beri beri;" and I will therefore
proceed at once to the description of the mature Rhabditis, which presents such
considerable differences from Dochmius that there would be no difficulty what-
ever in distinguishing the two species, even were they to be mixed together
in a single tray. As far as I could make out, the emigration from their original
home in horse-dung, on to plants generally takes place just before the distinc-
tion between the sexes first appears, that is to say, at a stage when the genera-
tive gland has already attained considerable dimensions, but at which the future
sex cannot yet be determined.
The most distinguishing character of the Rhabdites, after their migration
from the dung in which they were born on to forage plants, is the possession of
a peculiar mouth armature, specially suited to subserve their needs in this new
situation. This consists of a sharp, protrusible, chitinous style, which appears
to be hollow, and to consist essentially of a prolongation of the pharynx. With
this structure they are doubtless able to pierce the delicate cuticle of the plants
that harbour them, and so to extract the nutritious juices contained in the cells
beneath. The pharyngeal bulb, at no stage very distinct, is reduced to a mere
widening and thickening of the posterior third of the pharynx, and shows no sign
C 2