140 
LECTURE X. 
work entitled 'Fauna Suecica^ as w-ell as in the 
earlier editions of his Systema Naturae, seems in* 
dined to admit the existence of this animal, and 
forms a genus for it under the name of Micro-!' 
cosmus. 
The genus Medusa contains a very remark* 
able set of marine animals, wiiich are generally 
diaracterized by their soft and almost gelatinous 
substance, their rounded and somewhat flattened 
shape, their semitransparency, and their numerous 
arms or tentacula. The species of this genus are 
extremely numerous, and often present an appear- 
ance in the highest degree elegant and singular. 
They are of various sizes, some measuring one or 
two, or even three feet in diameter, while others 
are of a size so diminutive as scarcely to equal half 
an inch in diameter. One of the most remark- 
able of the larger kinds is the Medusa Pulmo, 
which is seen in many of the European seas, and 
is most common about the coasts of Italy and Si- 
cily. It measures from one to two feet in diame- 
ter : the body is nearly hemispherical, concave be- 
neath, notched into several very slight or shallow 
divisions round the edge, and furnished beneath 
with a very large and curious apparatus, consisting 
