in Semine Mafculino. 163 
plentifully flocked with Life than that of 
other Animals : for more than ten thoufand 
living Creatures were feen, by Mr. Leeu¬ 
wenhoek, moving in no larger a Quantity 
of the fluid Part thereof than the Bignefs of 
a Grain of Sand; and in the thicker Part 
they were fo thronged together, that they 
could not move for one another. Their Size 
was fmaller than the red Globules of the 
Blood, and even lefs than the millionth Part 
of a Grain of Sand *. The Bodies of them 
are roundifh, fomewhat flat before, but end¬ 
ing fharp behind, with Tails exceedingly 
tranfparent, flve or fix Times longer, and 
about five Times more {lender, than their Bo¬ 
dies. They move themfelves along by the 
violent Agitation of their Tails, "in various 
Bendings, after the Manner that Eels or Ser¬ 
pents fwim : and fo me times their Tails are 
moved thus eight or ten Times in getting 
forwards the Diameter of a Hair. 
Their Shape and Form is fhewn Fig. VII. 
It is wonderful to confider the Minutenefs 
of thefe little Animals, and particularly the 
amazing Slendernefs of their Tails : which 
muflr, notwithflanding, be furnifhed with as 
many Joints as the Tails of larger Creatures, 
fince they are able to move them with great 
* dr can. Nat . Tom. II. Par. II. p. 61. 69. 286. 
Agility : 
