lias 
root of the penis is bent in a very wonderful 
manner, and grows broader at its extremity, e, 
where it unites with feveral other parts, amongit 
which the tefticles ff deferve our particular 
notice, on account of their fingular figure and 
conftruction. ‘They are of a pale brown colour, 
variegated with red; but the {perm contained in 
them is white, and that, as wellas the coat of the 
tefticles, appears thro’ the microfcope, as if made 
up of little globules. The vafa differentia, gg, 
next prefent themfelves. Thefe vefiels widen 
confiderably at a little diftance from their union 
with the tefticles, and refemble, as it were, the 
two globofe appendages of thefe parts, bb. There 
is fo little difference between the other parts, 
that I cannot diftinguifh them from one another, 
though I take the longeft of them, as appears by 
my drawing, 77; for the feminal veflels, and the’ 
others, which are more globofe for the proftate, 
kk. All thefe parts are of a delicate whitenefs, 
and they convey a feminal matter of the fame 
colour to the cavity of the penis, Thefe are all 
the parts I have examined in the male Fly, as it 
was the Worm alone, of which I propofed to 
take a full and accurate furvey. 
The female, on the other hand, is furnifhed 
with a double ovary, conftructed nearly in the 
fame manner with that of Herrings. But I thalk 
defer fpeaking of thefe organs, till the external 
parts of the uterus are defcribed. ‘The female 
hides its vulva, and the extremity of its uterus, 
under the two laft rings of its body, Fig. xvi. 
aa. The vulva confifts of three joints, the 
firtt of which is oblong, and hairy at its extremi- 
ty, 44, and is furnifhed in the middle with two 
little black horny bones, which help greatly in the 
protruding of this organ out of the body. ‘The 
fecond joint lies entirely within the firft, as within 
its prepuce. It is naked, or free from hairs, and 
it ends in a horny bone, cé, ‘The laft joint, 
which, properly f{peaking, conftitutes both the 
vulva and anus, is perfectly black, and is com- 
pofed of a horny bone, and a membranace- 
ous fubftance, with here and there a few hairs, 
d. Thefe parts of the Fly generally hang out 
of its body, on its quitting the Nymph-ftate, in 
order that they may dry to a proper confiftency ; 
they then void a drop or two of a fluid, which 
looks like water mixed with chalk, The ex- 
crements afterwards, thrown out from thefe 
parts, look little balls with tails to them, and 
confifting of a fubftance that very much refembles 
plaifter of Paris, / 
In diffeCting this Fly, I found it contained 
an ovary divided into two partitions, each con- 
fitting of thirty-two oviducts, with four eggs 
in each, one pretty large, Fig. x1x. a. and three 
imperfect ones 4; fo that the ovary of this fin- 
gle little creature contained no lefs than 256 
eges. Thefe eggs were white, oblong, and 
crooked ; the colour of the {malleft was wa- 
The. B © OpKy of. Nr Ay Ty GO BE ory 
tery. When viewed with a microfcope, they 
appeared to confift, as it were, of little glo-~ 
bules, and the oviduéts fhewed themfelves in 
the fame manner. All thefe oviducts difcharged 
their eggs into the uterus by two common paf- 
fages, and the uterus conveyed them out of the 
body by a fingle channel. I furveyed the other 
vifcera, or entrails lying thereabouts, but very 
flightly ; fo that I could only fee that the fat 
that had exifted in the Mite, was now almoft 
totally wafted away, and that the inteftines 
formed a great many more folds than they had 
formerly done, though they were grown con- 
fiderably fhorter, and lay now entirely on the 
abdomen. Nor were the eges yet perfect, 
tho’ the Fly I diffected was four days old. 
Flies are by nature of a very warm and luft- 
ful conftitution; fo that the female, imme- 
diately after its: firft appearance in this form, 
and before it has changed its gray colour, in- 
vites the male to copulation. In this a@, which 
lafts for a confiderable time, the male always 
gets upon the female; and in this fituation he 
is carried by her up and down like a man on 
horfeback. All this time the female keeps her | 
wings expanded, and extending her vulva to 
that part of .the male’s body, where the penis 
lies, thrufts it into the cavity of this organ, 
which does not, upon this occafion, fuffer any 
erection, And this manner of copulation ob- 
tains in many other kinds of Flies, and likewife 
in fome kinds of Hornets. It is very fingular 
to obferve how the male gently pats the fe- 
male during this operation with his body, and 
prefles himfelf upon her juft asa Cock does 
with the Hen, tho’ the copulation of thofe 
fowls is very {peedily performed, and that with- 
out any abfolute corporal conjunction. 
The Flies under our confideration, are very 
ftout and vigorous; fo that it is no eafy matter 
to deftroy themby drowning: after lying in the 
water a confiderable time, fo as to appear quite 
deftitute of life and motion, they will imme- 
diately recover on being expofed to the fun, and. 
fly off as brifkly as if nothing had happened to 
them. ‘They have two methods of fying; in 
the one their motion is flow and regular, and 
in the other it is rapid and diforderly. I fed 
fome of thefe Flies with new milk-cheefe fteep- 
ed in water, which they fucked up thro’ their 
trunk, or probofcis. This ufeful and curious 
organ is placed on the lower part of the head, 
a little below the horns, or antenne, and it con- 
fifts of three hairy joints. I likewife had the 
pleafure of feeing them lay their eggs in a 
piece of cheefe, and I found in a few days af-= 
terwards a number of Worms which had 
fprung from thofe eggs, perfectly refembling 
thofe of the firft brood that had produced the 
parent-fly. 
The 
