94 Da. SHAW, Defcription of 
black. Its motions are in every refpe& analogous to thofe of the 
Hirudo complanata, flagnalis, and oéfoculata, which are all three fuffi- 
ciently common in this country ; but the {mall fpecies now defcrib- 
ing feems to poflefs a greater degree of contractile power than the 
three former, fince it often affumes a fhape approaching to a circular 
outline. Its general motion is an uniform fmooth progreffion, which 
is occafionally varied - a circular motion, as if turning flowly on 
an axis. 
This little animal, iier being ient lis a few days in in a glafs of its 
native water, feldom fails to appear filled with 5 or 6 ova, of a very 
confiderable fize in proportion to the parent animal, and which are 
of a much ftronger and tougher nature than one would eafily 
imagine; fince, when taken out of the body, and prefled on a glafs, 
it requires a confiderable degree of force to break them. Their 
form is exaétly oval, and their colour a deep brown. The larger 
fpecies of the genus Hirudo are known to be viviparous; but the 
 H. oétoculata is (according to Linnæus) oviparous, and produces a 
peculiar fort of ovum, which it depofits on the ftalks of water 
plants, and from which the young is afterwards excluded. | It fhould 
feem therefore that this very fmall green Hirudo is oviparous alfo, 
and probably may depofit its ova in the fame manner. 
The remarkable colour of this diminutive fpecies is alone fuffi- 
cient to diftinguifh it at firft fight from every other fpecies yet 
known: asa trivial name, therefore, Hirudo viridis cannot be im- 
proper; and its fpecific chara&er may be comprifed with fufficient 
exaétnefs in a very few words, viz. 
H. viridis oblonga, extremitate acutiufcula. 
To the above account of the Hirudo viridis, I muft beg permiffion 
to add the extraordinary power of reproduction which the fmaller 
fpecies of the genus Hirudo are poffeffed of. This reproductive power 
is moft confpicuous in the H, /lagnalis, complanata, and oétoculata, in 
which 
