66 
CLASS L— ORDER IL 
Cells of distinct formation , but uniting together , and 
coalescing with the stem . 
Plant-like Polypidoms with a distinct stem , which is 
either simple or branching , very rarely articulated , but 
generally a hollow tube, filled with a gelatinous animal 
substance , into which the lower part of every polypus is 
inserted that inhabits a cell , whose situation, form and 
size vary with the individual that inhabits it . 
GENERA AND SPECIES, 
PASITHEA. 
Plaht-like Polypidom, a little branching, and ar- 
ticulated. Cells in threes or verticillated ; sessile or 
pedicellated at each articulation. 
The two known species, which form the genus Pasi- 
thea, bear so strong a resemblance to each other, that 
the naked eye can with difficulty distinguish them ; 
it is necessary to employ a glass to observe them well. 
Their substance is much more horny than calcareous. 
Their colour is a dull yellow, more or less deep. 
Their size varies from one to three centimetres. 
They are generally found on the fucus natans, or 
some other Thalassiophytes of the equatorial seas. 
They are rarely to be found in collections. 
