8
must not, of course, be mistaken for epithelium), and also some oblique bands ;
then a delicate homogeneous membrane which does not stain easily ; then several
layers of large cells which do stain easily and contain nucleus and nucleolus ;
and lastly the lumen, containing blood, debris, water, bacteria, or nothing notice-
able. I think that the outer coat is homogeneous, because I have observed no
cellular structure in it; but this may nevertheless really exist. The cells
beneath it have a diameter of about 30 µ when uncompressed and contain,
besides the nucleus, numerous refractive granules of different sizes which are
particularly large shortly after digestion. They often contain as well certain
irregular but definite bodies lying close to the nucleus, which may be of a para-
sitic nature; but I have never observed within them any of the granular debris
from the cavity. Often, on the outer surface of the organ and among the
branches of the air-vessels we find greenish, yellow or colourless globules of
a high refraction, from I μ to 10 μ in diameter, free or enclosed in cells, and
probably of an oily nature.
I have never observed gregarines in grey mosquitos—they seem to be
parasites only of the brindled genus—but the intestine is often packed with hosts
of monoflagellate organisms, about 6 μ in length, exclusive of the flagellum.
These may be seen adhering to the wall of the gut, but breaking loose and
swimming about actively on the addition of water. They have already been
described by me as swarm-spores (3).
2. Growth and Structure of the Coccidia.—I can now proceed to a descrip-
tion of the development of the pigmented cells. It will be useful to suppose that
a stock of grey mosquitos were fed on a sparrow with mature proteosoma on a
Saturday night ; and that at the same time control insects, whose larvae were
caught in the same drain and hatched out in the same breeding bottle, were
fed on a healthy sparrow, on a man with crescents, and on a crow with halteri-
dium, separately.
Thus, insects dissected on Sunday, Monday, Tuesday,
....
may be said to be dissected on the first, second, third ....
day,
respectively, after feeding.
As the insects were released upon the subjects, say, at 6 P.M. on Saturday
night and were not caught again until, say, 6 A.M. on Sunday morning, and as
they may have fed themselves at any time, or at several times during the night
it is clear that when they are killed the period after feeding will have a margin
of uncertainty of twelve hours. An insect killed between 6 A.M. and 6 P.M.
on Sunday, however, must have a period after feeding of between o and 24
hours ; and one killed between 6 A.M. and 6 P.M. on Monday must have a period
of between 24 and 48 hours ; and so on. This method is wanting somewhat
in precision, but unfortunately it is not easy to feed and capture a number of
night-biting mosquitos all precisely at the same time, and it is exact enough for
my present purpose.
First day—Sunday.—Taking a control insect fed on the healthy sparrow,
we dissect it in the manner described above. The stomach full of blood, with
the œsophagus, intestine, malpighian tubes and ovaries attached, lies before us
on the glass slide. With the point of a needle we open the side of the organ,
and the contained blood runs out freely into the water of dissection. On a
cover glass being now applied, its weight drives out almost all the rest of the
blood through the rent we have made in the containing wall, and on holding the
slide up to the light, we shall see the oval tissues of the stomach lying com-
pressed, white and almost free from blood in the midst of the dark red-brown
mass of its expressed contents. We can thus easily examine with the highest