$ SEMINAL VERMICULI. tT. 
corpufculum, without analogy to a tail or any 
other member, and entirely foreign to the fper- 
matic vermiculus. I have always found, as has 
been fhewn in the firft chapter, that the appen- 
dage has every characteriftic of an actual tail. 
Tt has the fhape, and the diameter always be- 
comes greater on approaching the body to which 
it is united, fo as to form one whole, as is feen 
in tailed worms: and the vermiculi alfo ufe the 
tail while fwimming through the fpermatic fluid, 
bending it firft to one fide, then to another, 
and in every different direction as aquatic worms 
are wont to do while they fwim. I have feen 
this innumerable times, and in the moft diftingt 
manner ; fo that I muft difcredit my eyes, if I 
think or write differently. Y 9a 
It is true that microfcopic obfervation on the 
tail of human feminal vermiculi is the moft nice 
and delicate of any I have made : it demands the 
greateft care and the ftricteft attention, The tail 
is wonderfully flender, and at the fame time tran- 
fparent ; whence, too ftrong light confounds it 
with the feminal fluid, fo that we entirely lofe 
fight of the whole. In the firft place, the choice 
of light, adapted for obfervation, is of the great: 
eft importance. The direét light of the fun is too 
powerfyl, as is that of a lamp, unlefs it is mode- 
rated by fome method. That which I have found 
moft fit for this fine obfervation, is the light ofa 
window 
