Ephemeri vita, or, The natural history and anatomy of the Ephemeron, a fly that lives but five hours written originally in Low-Dutch by Jo. Swammerdam ...
Swammerdam, Jan, 1637-1680., Tyson, Edward, 1650-1708.
Figure 3.

In the third Figure is repre∣sented the Worm Three years old, in length about 2½ Holland inches, but among those of this age there is much difference be∣between the length and thickness of the one and the other. The Worm here represented is a Fe∣male, and one of the smallest size of that Sex, which difference of Sex is to be discerned in the eyes, which in the Females are much smaller than in the Males; the Wing-cases, in which the wings are inclosed, appear now very plain, notwithstanding the upper pair so much cover the under pair; that at first sight they are not vi∣sible, except the uppermost are lifted up; here is also represented very clearly—the 6 Gills, on each side of the body—turned over the back, whereby the undermost Ten Finns of each side are made visi∣ble; at this time these Gills are never without-motion, yea even Page  [unnumbered] out of the water, wherefore some have judged that the Worm swims by the help of them: But I judge that is performed only by the Finns, as I have named them, placed under them; while for ma∣ny reasons I believe that the up∣permost, which I name Gills, and which agree with the Gills in Fish, do cool the bloud in this Worm, as is done in Fish.