116 The BOOK of 
Moreover, it muft be well obferved, that the 
head and legs are ftript of their skin in the 
fame manner as we draw our feet out of our 
fhoes, or our head out of a narrow cap. But 
-as to the other parts, namely, the firft and fe- 
cond pair of wings, the skin is drawn off from 
them in fuch a manner, as that the infide is 
turned out and the outfide in, as we invert a 
limber pair of gloves, the inward furface or 
infide of the fingers being pulled out. At the 
time when half the skin is drawn off the wings, 
thefe infects are as helplefs captives, and fixed 
in that condition, fig. x11. they even lie for 
fome time without any fenfible or remarkable 
motion, The reft of the body is likewife by 
this fecond change extended and becomes much 
longer, and the tails become a third part longer 
than they were after the firft change. So that 
the tail and legs which were made, under the 
firft change, a third part longer, are now again 
as much more lengthened; but this holds‘ more 
perfectly in the tails than the legs. For, as the 
tail confifts of hollow rings which are capable 
of being drawn out from each other, hence its 
extenfion is much more confpicuous than that 
of the legs, becaufe the latter only lay folded 
in the skin, but are now extended fully to their 
length, and nothing more. It is moreover 
to be obferved in regard to the tail, that its 
hairs, which were planted very'thick in the 
Worm of the Ephemerus, are placed more re- 
mote from one another when it flies, and they 
alfo become much finer and thiner, fince they 
likewife caft their skin twice, and appear iffuing 
out of their hairs as out of little fheaths, 
The Ephemerus having thus partly thaken and 
partly drawn off its skin, by inverting or turn- 
ing it infide out, being now perfect, fecks 
again the water, on the furface of which it flies 
and beats up and down gently and quickly, 
and, as it feems, wantonly fports and plays, 
and then refts again, leaning on its tails, and 
ftriking its wings againft each other. Whilft 
the Fly is thus in motion on the furface of the 
water, and loofely playing with its wings, its 
tail, which is hollow and full of hairs, very 
eafily fupports the body; for, as it contains air 
in it, it is therefore carried lightly upon the 
furface of the water, and does not fink under 
it. Something like this is obferved in feveral 
other infects, which will continue in the fame 
manner, fufpended on the furface of the water 
‘by the help of hairs, within and between 
which the air is detained, as is the cafe in the 
Worms out of which Gnats and Gad-Flies are 
produced. The air, however, does not always 
continue in the tails of the Ephemerus, but 
fometimes comes out of it, and may at any 
time be let out if they are pricked with a nee- 
dle, in order to dry and preferve them; for 
then they generally become corrugated or wrin- 
NEAT URE; ‘or, 
kled, and fink or fall together. There is alfo 
another reafon why the Ephemerus flies thus 
lightly on the furface of the water, and that 
is, becaufe it carries a {mall bladder full of air 
in its body ; unlefs we fhould rather incline to 
think that it is the ftomach of the Ephemerus, 
which is then inflated or blown up with air. 
But I fhall affirm nothing certain concerning 
this matter, fince it is not fufliciently clear to 
mylelf, 
The male, fig. vi.as appears tome, changes 
its skin twice, but the female, fig. viz. only 
once. Ido not, however, advance this as un- 
doubted truth, fince I have not yet confirmed 
it by a fufficient number of experiments. For 
this reafon, if it be thus, we obferve that the 
tails of the female are a third part fhorter than 
the tails of the, male. Eefides, another more 
remarkable difference is, that the eyes in the 
male are twice as large as in the female. A. 
third difference is, that the yellow colour of 
the body in the male approaches more to red 
than inthe female. The male likewife has, 
befides his two larger tails, four appendages, 
like crooked little tongues, which cannot be fo 
diftinétly feen in the female. Thefe are the 
great differences of the two fexes. 
The Ephemerus does not engender either in 
the body of the water, or on land, nor in the 
air, but the female throws out her eggs on the 
furface of the water, and the male afterwards 
cafteth his {perm upon them *, and he has 
probably, for this purpofe larger eyes given him 
by the all-feeing Creator, that by means of this. 
advantage he may eafily find out the eggs of 
the female wherever fhe has dropped them. 
As therefore a great many {pecies of fifh with- 
out coition throw out their eggs into the bot- 
tom of the water, to be afterwards impreg- 
nated by the male, fo the Ephemerus throws 
its {perm into the water. ‘Thefe eggs, when 
caft out, are not collected and concreted toge- 
ther in the form of a perfect ovary, like 
that which the Ephemerus carries in its body, 
but are feparated and difperfed from each other 
as they are in fifh. That the Ephemerus while 
a Worm does not perform the bufinefs of coi- 
tion in the water, is manifeft from hence, that 
it does not come out of its cells only at the 
time it is to caft its skin. Nay, if it fhould 
go out of them, as it fometimes does through 
neceffity, or to breathe frefh air, yet it is by 
no means able to do any act to propagate its 
{pecies in the water, for it cannot remain fuf- 
pended in the water but while {wimming, and 
it finks immediately to the bottom when it has 
a mind to reft in it: but at the bottom it has 
no fixed refidence till it has made a new cell or _ 
habitation for itfelf. To thefe we may add 
another, the ftrongeft argument of all, that is, 
that no infect ever enter upon the bufineds of 
* This, though common with fiih, is ftrange among the infect kind ; but in the whole compafs of natural hiftory nothing is more 
varioufly performed than the impregnation of the eggs, nor any thing {o little underitood ; it feems, they may not only be impreg- 
nated by a male fperm caft upon them when laid by the female, but even by the fame fluid caft at random while they are yet 
in the body of the female. 
Monfieur Demours is particular in his obfervation of the water Newt, the male of which has no 
penis, but difcharges his fperm in the water near the female, whofe eggs, though none of the fperm abfolutely enters her body, 
are fo impregnated, 
- 
generation, 
