ZOOPHYTA BRITANNICA. 
ORDER IV. 
Z. ASCIDIOIDA. * 
Character. 
Polypes aggregate , the mouth encircled with filiform ciliated 
retractile tentacula ; a distinct stomach , with a curved intestine 
terminating in an anus near the mouth ; ova internal . — Polypi- 
doms very variable , — either horny fistular and confervoid , or cal- 
careous , membranous , or fibro- gelatinous, formed of cells connected 
and arranged in a determinate and usually quincuncial manner . 
Observations. 
In the preceding orders we found reason to conclude that 
the polypidom of the Hydroida was a sheath disconnected, or 
at least not in organic union, with the soft pulpous matter which 
it invests and protects ; that the corresponding part in the Aste- 
roida, become an interior skeleton or axis, held the same rela- 
tion to its polypiferous crust ; nor was this relation altered when 
the polypidom had again, in the Helianthoida, assumed an ex- 
ternal position, forming an integral part of the epidermis. In 
all these instances the polypidom appears to be unorganized, 
and when once formed, beyond the reach of change from either 
the polypes or its own inherent powers ; *[* but in the present 
* This order corresponds with the Polyzoa of Thompson, the Bryozoa of 
Ehrenberg, the Bryozoaires of Milne- Edwards, and the Cilioerachiata of 
Farre. Our order Hydroida Farre designates Nudibrachiata, thereby indicat- 
ing the absence of cilia on the tentacula ; and Milne- Edwards les Sertulai- 
riens. His Alcyoniens is synonymous with our Asteroida ; and the Zoan- 
t aires with Helianthoida, but Farre unites these under the name of Antho- 
zoa, borrowed from Ehrenberg. 
“ Unorganized non-vascular parts are produced by an organized matrix, 
and grow by the continued deposition of new matter on one surface.” Muller’s 
Elements of Physiology, p. 384. 
