66 



CLASS 1.— ORDER 11. 



Cells of distinct formation, hut uniting together, and 

 coalescing with the stem. 



Plant-like Polypidoms with a distinct stem, which is 

 either simple or branching, very rarely articulated, hut 

 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. 



Plant-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. 



